I think the question is why would that block be any more of an impediment to leaving Ridley on hard than on normal, since the unknown item needs to be collected before departure anyway.
...on hard, it's harder. Thus, you might want to leave and come back with more items to kill ridley with. So the block's not there so people can, uhm, leave.
?? You don't mean the vertical room at the right side, do you? Because that's accessible via the room to the right of the elevator, by the route normally taken for low-percent runs. You just can't leave that room until the block is gone, because you get to where the platforms and ballsparks (what are their actual names?) are by falling through crumble blocks.
I think AJ is referring to getting the super missile from Imago and/or going through the green door to the left of the elevator to collect other stuff if necessary. As far as I know you can't actually leave Ridley and return to Norfair until Ridley is defeated because the wall doesn't crumble to let you get to the broken Chozo statue part until after that. Although it seems just as likely to me that someone could end up underpowered for the Ridley fight on normal as on hard so it's a somewhat arbitrary choice to have that block there on normal/easy but not hard.
theres really no point in leaving because, as it was said, you cant. and anyways if you cant handle Ridley on hard then come better prepared or dont play hard.