(SPOILER)Yeah I can't think of an elegant way they've could revealed it later. I do think showing us what happened is to make us feel for Jessie as she doubts herself and make her more tragic as a character, plus also make us, the player, more angry toward Shinra when the propaganda wheel starts turning. I do think there was a bit of a missed opportunity after the Reactor 5 to develop Jessie even further. After all she went through the trouble of getting weaker blasting agent to avoid a repeat of Reactor 1. So surely she would have similar doubts if Reactor 5 went up the same way. I guess they could maybe have dropped the revelation before the Air Buster fight after starting the remote detonator on the bomb - Heidegger could've gloated about it being just like Reactor 1 again. But then I dunno if that would have lessened the impact of Jessie's arc before that point or not.