'course it'll be valid, don't worry, it's been discovered a very long time, but as far as I know is that we haven't figured out what causes this so there's many ways to trigger it. edit: wait I don't really sure if it's allowed in NMG runs, I think it is, but if you're still worried you can go discord and ask this

basically do this https://b23.tv/kLCoZmT

Just an AI break, nothing new, there's even a consistent setup to do this. Load the autosave, then you just walk to the left rear railing after pushing Ashley up and look at the door that the enemies come out, make sure you can see each other and Leon isn't moving when they first come out. And after triggering this don't open the menu or suitcase or do anything that'll make your game pause. Don't know how but it just works.