Sure, and if they just said "we'll close tickets for anything to do with theming" or similar, it'd be fine, but instead we get:
> We understand the need for distributions to stand out. However, we urge you to find ways to do this without taking away our agency. We are tired of having to do extra work for setups we never intended to support, just to have that used against us when people tell us the breakage from theming is “not that bad”. You are not doing this to Blender, Atom, Telegram, or other third party apps. Just because our apps use GTK that does not mean we’re ok with them being changed from under us.
> Since you are shipping the GNOME platform, we assume you want this ecosystem to be healthy. If you do, we ask that you please stop theming our apps.
I'm sorry but just becuase you make some software that works together you don't get to designate it a platform and decide you should control it. Not in the free software world, at least.
Debian et al. aren't "shipping the Gnome platform", they're shipping package managers that can install many things including a bunch of Gnome software (and vastly more non-Gnome software). A very large proporrion of it can be themed or customised in some way.
Some people use Gnome "stock" but don't install or use any of the Gnome apps, others use aspects of the Gnome WM but without the default panels and interfaces, others install the whole lot, some run Gnome software but with a totally different WM or desktop environment, and then there are things like Regolith [1] which use some Gnome software but are pretty unrecognisable compared to a default Gnome install.
Gnome devs are just writing software. Their desire to deifne and own and control a platform is their problem, not ours.
[1] https://regolith-linux.org/