A big difference with your examples is that basically every adult was already using a smartphone. So adults don't just jump to conclusions that it's evil. It's more like... "Smartphones are useful"

I remember when I first saw little girls with Blackberries. It was quite strange.

It always depends on your position and their position, but by the sounds of it... I'd say it's too big for a simple "review this".

I'd ask for them to write their thought process, why they made the decisions they made, what the need for so many files and so many changes. I may ask for a videoconference to understand better, if it's a collegue from work.

By now hopefully you should know if their approach is valid or not really. If not sure yet, then I'd take a look at the code, specially at the parts they refer to most importantly in their answer to my previous questions. So not a detailed review, a more general approach, to decide if this is valid or not.

If it's a valid approach, then I guess I'd review it. If not, then give feedback as to how to make it valid, and why it isn't.

Not valid is very subjective. From "this is just garbage", to "this is a good approach, but we can implement this iteratively in separate PRs that will make my life easier", again, it depends on your and their position.