FWIW, I can do the same with KDE on Xorg with Gentoo Linux.

Since the introduction of the XSETTINGS protocol in like 2003 or 2005 or so to provide a common cross-toolkit mechanism to communicate system settings, the absence of "non-integer" scaling support has always been the fault of the GUI toolkits.

> I think your experience comes from GNOME which lacks behind in this regard.

When doesn't GNOME lag behind? Honestly, most of Wayland's problems have been because a project that expects protocol implementers and extenders to cooperate in order to make the project work set those expectations while knowing that GNOME was going to be one of those parties whose cooperation was required.