Yeah, if that’s what OP means (though that’s unclear), I’m not sure why OP thinks it’s a bad thing. It’s a good thing.
Or maybe OP means Firefox crashes more or something. In which case I can only say that hasn’t been my experience.
My experience has been, however, that Firefox is quite usable on a Raspberry Pi 4 while Chromium is far too resource hungry to be usable on that platform.