It is but I don’t see that as a bad thing on this occasion because diversity in rendering engines, even if some are opinionated, is better than a Blink monoculture (or Trident before it)
User agents are explicitly allowed to have their own preferences, that's the whole point of having multiple browsers in the first place. If you want every browser to be identical then why even have more than one? Browsers don't even have to have display favicons if they don't want to.