Fair enough. I suppose people looking for survivors could've already been climbing the plate before Cloud and Tifa ever got to Jessie, got to Biggs, saw him wake up enough to tell them she was near the top before passing out again, and got him out while others went further up, getting her while the others were fighting the Turks, then heading back down just as the pillar was starting to go up and getting out of the sector just in time. We don't see what's going on in the rest of the tower after Tifa catches up to Cloud and they move on, all we see is what they're doing. So I guess it's possible. Sorry, just trying to figure it all out. As for the gap in the stairs, I'm sure the people would find a way to cross it if they knew someone's life depended on it.