openSUSE used to have the /home folder (so, not a specific user subfolder) on a different partition as the default setup some years ago, with 40 GB for the root partition.
They changed it, because it meant people's root partitions would sometimes fill up from the snapshots being stored there and that's really annoying to recover from.
Not only can a full root partition irreparably damage your Linux system, it also meant that people would try to uninstall packages to free up space, which wouldn't actually free up space, because those packages were still contained in differential snapshots.
To actually free up space, you have to either delete old snapshots (so that there's less difference to your current install) or delete intermediate snapshots where you happened to install a load of packages, which you uninstalled afterwards.
I'm not asking this for limited space. My long term purpose is having just my home with granted space and luks encryption (and obviously decryption on login).
Hmm, as in you only want your home-partition to be encrypted, nothing else? Because you can do filesystem encryption for the entire btrfs (including both root and home) and that works perfectly fine.
Not sure, if it uses LUKS for that, but there's an option in the installer for encryption...