With little research your claims of things that the GNOME developers are supposedly trying to do are quickly proven false and aren't based on facts but rather on beliefs that you have built up out of a dislike of how GNOME handles things.
For example, Kitty also allows resizing in this way, regardless of Window Manager, because this is something that X11 APIs allow.
This completely derails your claim that "Gnome Developers really want to push as much development onto the individual application makers" because in reality this just shows that GNOME decided not to arbitrarily override X11 APIs in the position of a Window Manager and Compositor.
Time and time again I have seen that your opinions regarding how GNOME does things come from a place of dislike or possibly even hatred, but not of research of how the features that you're criticizing work. This is in stark contrast to how thoroughly you often research other topics regarding how GNOME runs things in terms of Ideology or Governance over the project.
GNOME-Terminal was programmed to (by default) use X11 APIs to adjust the window size in steps according to the grid that the Terminal window has. This was a conscious decision by GNOME-Terminal developers and has nothing to do with Mutter.
Please note that Tilix isn't based on Gnome-Terminal, it only uses GNOME's Terminal library that happens to also be used in Gnome-Terminal. (see: VTE)
If you look at the Source-Code and official website you will soon notice that it is mentioned nowhere that Tilix is supposedly a Gnome-Terminal fork.