Do you test as much on FF as on Chromium based browsers, during development, as well as in quality assurance steps? I could imagine, that some devs are looking at it in Chromium (or even Chrome shudder) all day, while implementing things, and then just having to tick a checkbox for FF "Yep, seems to work.". Which would of course lead to a Chromium-centric code.
Being one of the ZetaOffice (and LibreOffice) hackers, I use Firefox as my primary browser. And I really don't like using software only Google knows how to support (=> Chromium). Sometimes I even think about migrating to SeaMonkey
But for example, you unfortunately can't properly debug multi threaded WASM code in Firefox.
Have a look at the Firefox developer tools' debug tab with this page opened. And it will list the threads (web workers) named with some randomized UUID. Impossible as a daily development driver :-/
Most devs here use FF as their daily driver - that said, if you need to debug an emscripten-compiled c++ WASM application in the browser, then it's either printf-debugging, or Chrome + the C/C++ DevTools extension. Additionally, the overall QoI for running WASM binaries appears quite a bit better for Chrome. Both issues tip the scales currently, in favour of Chrome (sadly).
Do you test as much on FF as on Chromium based browsers, during development, as well as in quality assurance steps? I could imagine, that some devs are looking at it in Chromium (or even Chrome shudder) all day, while implementing things, and then just having to tick a checkbox for FF "Yep, seems to work.". Which would of course lead to a Chromium-centric code.