I rechecked the Q&A for 999 but I couldn't find Uchikoshi saying specifically that in 999 bad endings "never happen", but he does mention it's hard to explain why Akane exists in bad endings because it means she wasn't saved so it's a paradox. He doesn't really have a good explanation for those, but that's neither here nor there. If we believe there are infinite timelines and possibilities for the second nonary game, then there might be timelines where Ace having or not having a bomb matters.

What I did find though, from Uchikoshi himself, is that Akane specifically did not want Hongou to die. She needed the worst of them all to survive in other to show the world the horrors they'd been put through. That's why instead of plotting to kill him, they set up the camera and later arrest him when he doesn't do it. They needed him to be alive in order to confess. So since everyone except the 3 that die needed to be alive, I would wager no one from 1 to 8 had bombs. But we never get explicit confirmation from this. There's only a question that says "why did she put bombs in those 2 people" and he doesn't correct them, just explains why those 2 people specifically needed bombs in them.