Today's swap also is not preallocated by the user. It is entirely handled by the OS itself. If it needs swap space to hibernate it will go ahead and allocate it itself.
It does? Last I checked Linux doesn't do dynamic swap sizes, and while Windows has dynamic swap sizes it has a separate big non-dynamic file for hibernation. I have no idea what MacOS does.
on my thinkpad with fedora hibernate works fine. i use it frequently. i even use it when for an unknown reason my usb-c headphones stop working. i don't know why. but after hibernate they work again. somehow waking up from hibernation fixes the problem