I suspect there will be more demo downloads, but fewer total (non-refunded) purchases with this modal. The question is where do you apply friction, before download or after 90 minutes of gameplay.
I'm also generally concerned with demo-hacking. Putting all the novelty in the first 90 minutes. Placing one large cliff hanger or achievement near the 90 minute mark. Building a starting place that takes just over 90 minutes to get out of. I do get the impression PC devs are aware of the 120 minute mark and try to make the first two hours strong. This lowers that bar.