I don't remember the exact reason but I'm pretty sure it was because the scene was not vanilla, i.e. custom text lines that would have to be stripped and stuff. its really been a long time. a year, maybe?
and tbh, I never cared enough to test it again. Nowadays I need to know who says the line in the field script, under what circumstances and then what is next / after. Makou Reactor is just the only thing that does allow editing that way reliably.