I don't completely buy that, I think the amount of how 'real' it is really depends on how the magic of the real world works. Like, are the creations sentient beings with thoughts and feelings, or are they literal programmed NPC's executing their code? Everything you see makes it seem as though they are 'real'. I haven't gone to beat the final boss yet, but I'm not sure if anything in the ending will answer that definitively or change my mind. The obvious solution that would solve everything in my view would be kick all the painters out of the world and just allow it to exist as it was, as opposed to erasing everything. This would require them to have the willpower to not jump back in again, so the two women just need to learn some impulse control.
I don't speak JP and I don't really even like her, but I watched most of Koyori's first stream yesterday and her emotional reactions were pretty good. She should be getting to the ending of Act 1 tonight: