Okay, so! There are two different things I could see you meaning with this and I'm not sure which one is right, so I'll comment on both.
If you're saying to play out the established HX choices (for instance, you've got a Brainer and they say that they've watched someone sleep, so you play out that scene):
I could see this being interesting, but it doesn't feel like it's particularly necessary all the time?
With some things it could be pretty cool, like "they left me bleeding and they did nothing," or "they got me out of some serious shit." I could see the appeal of going through and seeing what, exactly, those situations were like- and it would give the players a better understanding of how their characters fit together (or have done in the past); Definitive things that the other did, rather than knowing "this is what happened in a blank discussion and so my character does not like yours/is grateful to yours/ect." depending on how much detail the PCs themselves come up with; I've had PCs who spend several minutes in-session or time between sessions discussing how their characters knew each other and what happened specifically, just as I've had ones who keep it vague. Note also that there's nothing stopping you from asking questions in these stages as well, if you want to dig into the meat of it a little more! That, in many cases, is probably all that's needed.
For other options it might not be as interesting- "they've slept in my presence" can be interesting in knowing what context, but if one character unknowingly did so (and there's no other real twist or thing to it other than that) then it's probably going to be a bit boring to play out rather than just asking the PCs, "Hey, that's cool, so when did you do this? [Hardholder name], where were you that [Brainer name] could watch you? Or did they sneak in to do so? Did you ever find out?" and so on and so fourth.
Same with the Hocus seeing someone's soul- in a game I've been MCing, our Hocus and Angel decided that the Hocus had seen her soul just passing by. A kind of "glancing at a crowd, seeing something that stands out strongly" sort of thing, which wouldn't have much basis for roleplay or anywhere to go to play it out. Other times, you could have that particular line be much more interesting- seeing their soul in a less physical way, or being in a situation where they saw who the person really is when in a dire situation. Those could be interesting to play out, depending on specifics.
For that option I could see it being cool, basically, on a case-by-case basis. Note that this would also be complicated by the fact that not all people will have playable scenes, or at least not playable scenes that would be interesting past a base-level of "this happened and these are the circumstances" (which should probably be established before going into the scene in the first place.) This can leave certain PCs out, and become boring for those that don't get any screentime.
If that was your intent I could totally see doing it, but I'd say you should apply it less as "play out all of them" and more as "play out the ones that tug at your interest, specifically" (and of course ask the PCs if they want to do so.)
If you mean scrapping the current HX system altogether to instead throw each PC in a scene together and watching it play out (or using the current HX system and spring-boarding off into a scene with those characters):
This could be alright as long as you know something about the character's histories with each other to begin with, or the PCs can tell you quite plainly how they work together.
Certain characters may be close friends (and would be suited to a scene that gives them opportunity to show how their friendship interactions are, or showing what they do for each other in times of need, ect.) others may only know each other through work (and would therefore not make sense to be shown in a scene outside this area) while others come together only with the presence of other people; Friends-of-friends and all that (so it would not make sense to put them somewhere where they were hanging out by themselves without a reason for it, at least not off the bat.)
I guess in short it depends very highly on the MC's understanding of what the PCs want out of their own relationships (which can be said even for starting up a game in general- always ask plenty of questions), and the PC's ability to even come up with this stuff on their own just based on what little introduction they've had to the other characters (assuming you're scrapping the HX system altogether, which is what I feel like you were implying? I might be reading wrong!)
There are also people who are going to be bored/annoyed with playing out things that don't have to do with the quote-on-quote ""real plot"" (which for some can be explained with "this is setup to the plot," but for others that will not be listened to) so that's something to keep in mind as well, if you're saying you're going to be playing out scenes that happened in the past.
In general I think a lot of it has to do with the particular group of players that you have; The HX assigning as it is now is very helpful to get things started, though, so I wouldn't recommend scrapping it completely (particularly for first-time players.)
A last note I would give is that there's not much stopping you from going through HX as normal and then doing this already- most starting sessions I see have that sort of feel to them. "Let's give a chance for each character to interact one-on-one" as the first session is often a well-used thing, especially because it makes an easy setup for things to come (whereas playing out past scenarios that may have very well happened years ago may not do much for you heading forward other than saying "hey, that's cool.")
I think that, in short (regardless of what method you're using) you should probably do this if you feel that it'll add something to your game, without taking away anything else. I'd probably go case-by-case instead of making a mechanic out of it, unless you really think it'll improve yours and your player's experiences.
That's all my thoughts on it, anyway! I hope at least one of those two inturpritations of what you were saying was correct, but if I was reading wrong feel free to tell me.