Acredito que o escalonamento DPI é responsabilidade do servidor Xorg.
A página do ArchWiki sobre o assunto também menciona isso:
GTK very often overrides the server's DPI via the optional Xresource Xft.dpi. To find out whether this is happening to you, check with:
$ xrdb -query | grep dpi
With GTK library versions since 3.16, when this variable is not otherwise explicitly set, GTK sets it to 96. To have GTK apps obey the server DPI you may need to explictly set Xft.dpi to the same value as the server.
Parece que alguns gerenciadores de janelas que lidam com mudanças de DPI também o fazem através do Xorg.
The Xft.dpi resource is the method by which some desktop environments optionally force DPI to a particular value in personal settings. Among these are KDE and TDE.