So, a lot of people are going to be going "She had to give Okabe his Kyouma persona, so that's a plothole since she only does that on one timeline!" but that's not the case. Remember the scene before it, when Suzuha and Kurisu are talking about causality? How even after getting hit by a fucking truck, Okabe won't die, because attractor fields won't let him die before his time. Same concept here. There is likely an attractor field that causes him to, at that moment, become Kyouma. What Kurisu does here is smart though. She does what Okabe did in the last episode of the anime. 'Change the past without changing anything'. She inserts herself as the cause of Kyouma, which is different. Now instead of Okabe becoming Kyouma because of something he thought up on the spot, it's because of her. It's an anchor. It's different. Now, if he ever starts to slip to the R line, he just has to think about that major difference. No plot hole, the rules of time travel are still solid. It's a surprisingly well thought out loophole for an add on movie.