A properly built tablet OS UI would also have those differences in the OS that make it more than just a larger phone screen, which so far seems to be most of what the foldables are doing with a gimmick thrown in here or there.

iPadOS may not fully be to the point of being an OS UI that really utilizes the benefits of a tablet sized device, but it does have elements that are unique to it that would not really make sense on a phone.

That being said, if your tablet use case really is just a larger phone than a foldable would be great. But i know for myself the way I use my iPad it would not be a suitable replacement. Especially not now, maybe in 5+ years once someone figures out how to make an OS that actually manages different ways of interacting with it in different form factors work, but that has yet to happen.