It’s really not ambiguous. Anyone can fork Firefox, make any changes they want, and release it with different branding. This is the goal of open source.

The term you’re looking for is free software. By making this change Firefox is no longer respecting the freedom of their users. That’s the “F” in FOSS. It’s possible for Firefox to remain open source without being free software.

There is an android skin in the settings, not as fleshed out as the ios one but it gets rid of the uncanny valley effect for me