I’m curious about this, because over the past decade or so, large parts of GTK’s cross-platform ability have been
actively sabotaged. It used to be possible to style it to look native on Windows, with some feel problems but mostly comparatively minor. Now, well, no one has quite managed native look (whether or not it’s possible, and certainly I’ll allow that “native” is very ill-defined on Windows these days), and feel is
way off in important ways because they’ve deliberately removed a number of important pieces, forcing GNOME HIG conventions. (Things like how they basically force GNOME’s style of overlay scrollbars these days; also keyboard stuff is regularly hopelessly wrong.) The GTK/libadwaita separation is a lie. The GNOME Foundation co-opted GTK and deliberately scupper it for everyone that’s not GNOME (whether on Linux or for other OSes).
So I’m curious whether this sort of patch would be accepted. Assuming reasonable quality of patch, it pretty obviously should be if you want to be a cross-platform toolkit that doesn’t feel massively out of place, but without knowing what position or connections Paul Rouget may have, I’m honestly sceptical that such a patch would be accepted.