Maybe this will help make it a little clearer: In Michael's example, I read the initial bit as the GM making a move for whatever reason - probably just because everyone looked at him to see what happened, but maybe even due to a failed roll.
The GM establishes a fictional thing: The ogre's about to smash you! What do you do?
The player can't just ignore the established fiction and Hack and Slash. At the least he has to accept that an ogre just bashed him and take the consequences.
The ogre is doing something, to which the player may or may not react. After that, the player might do something like Hack and Slash. If the player gets a 7-9, that might mean that he's opened himself up to another attack from the ogre - uh oh!
If Michael's example didn't start with the ogre swinging, the player could Hack and Slash no problem. The defining characteristic is that we know, fictionally, that the ogre as a swing in motion to the fighter. If the fighter sucks it up it might play like this:
Player: (Thinks for a second, realizes that he has +1 forward now and would rather save it for the attack) "Whatever, I take it. I bring my shield up to deflect it while attack up under his defenses."
GM: "Okay, X damage as the tree trunk the ogre is wielding bounces off your shield. It sounds like you're Hack and Slashing then?"
Player: "Hell yeah! Dang, even with the +1 I got a 9. "
GM: "Well, you deal your damage, but the ogre gets in a strike too. You get in under his defenses sure enough, but after you slice him he flinches away and brings his knee up into you, X damage."
If the situation started differently, say with the ogre attacking someone else, it might play out like this:
GM: "The ogre smiles as he knocks you off your feet and you go sailing a few feet through the air, landing on your back against the edge of the cliff. The ogre starts moving towards you, smacking his club against his hand. Ajax, what are you doing while Omar is getting whalloped?"
Player: "The goblins are dead now, so I'm focusing on saving Omar. I step between him and the ogre and slash at the ogre's legs, try to make him less mobile."
GM: "Sounds like hack and slash to me."