wat happened
It's more talking about how Tsukishima's Book of The End works as in truth, while he can insert himself into people's memories, the best way to make it easy for himself is to replace someone else in their memories and use that as a basis and further expand from there.
While we do see him helping against Rukia and Aizen, he also replaced Orihime's brother in her memories and replaced Chad's Grandfather in his(This is also when Tsukishima started explicitly fucking with those memories they nearly had a mind break).
So in truth, it's not an actual Genjutsu or any of that sort as Tsukishima explains before he repairs Ichigo's Bankai to be healed he actually creates a whole ass branch of time as to him, those events are genuinely real as much as they are to everyone else he infects. It's why me and Adamant explicitly state Book of The End is the strongest Bleach ability period, even above the wanked Almighty.