'Make Apocalypse World seem real' seems like the more relevant agenda. If your Maestro D' is asking for something that seems actually impossible, or stretches the boundaries of the world as you understand it, you should probably address that when they are first using the move -- not by messing with the result of the 10+, after the fact. Like, if there is no suggestion so far in the game that someone owning a functioning tank is even a thing -- like so far you are in some sort of low-tech jungle region full of spear-hunters or whatever -- then that sort of request seems outside the boundaries of the fiction. But if this is a world where there's lots of scavenged stuff around, and military hardware (even of a lesser size) is around, then sure, why not.
It is obviously super not-boring to have somebody give you a tank, after all.
My feeling is that the move is specifically about allowing the Maestro D' to avoid having to use Barter to get what they want -- the flip-side of that is that if they are asking for something that could not reasonably be acquired by Barter (up to and including like, a million barter) then maybe I should be concerned. But other than that, go for it.