Ohhh, that's what it's for! I use it for scaling x11 apps with the run_scaled script that's shipped with xpra (:
(I'm on Devuan Daedalus 5.0, ~= Debian Bookworm 12.0.)
(I currently use 'xzoom' to scale X11 programs, but it's a little kludgy.)
EDIT: Single quotes for all program names. Bookworm, not Bookwork.