It does, especially when you want some influence on the scaling. E.g., if you want to fit more content, or less content, than the exact 2x scale. (IOW, whenever downsampling/upsampling is on.)
Sure, but the premise of this thread is that Apple increasing the physical resolution is nice because it improves sharpness. That's moot for people who won't use the native resolutoin.
What Windows does is render to the native resolution. Elements that are properly aware of the scaling are just pixel-perfect. Elements that aren't or can't be, such as bitmap images or apps that are incompatible, are indeed resampled.
Like, if you have 12pt text and the scale is 100%, it gets rendered at 12pt. But if the scale is 150%, it gets rendered as if it were 18pt.
Agreed. A 16-inch display is too small for that to make any difference. If anything, if the idea is to edit(!) 4K content, which is indeed a typical use case on an MBP, you'd surely want a resolution larger than 4K, which is just completely impractical on such a small display. Just hook up a 5K or 6K display.