I'm not entirely sure whether it is more sustainable to maintain a separate rendering engine than to gradually build up Chromium expertise outside of Google.
With FloC, we now have a test case where we will see whether or not other Chromium based browsers can make independent decisions that go against Google's interests.
you can build all the expertise you want, it will not achieve much control or influence over what gets put into Chrome and therefore what power Google has to influence or just ignore web standards. The real power comes from voting with your feet and using a different browser altogether.
Building Chromium expertise could enable Chromium alternatives such as Vivaldi, Edge or Brave to selectively remove or override features that only benefit Google.
I'm wondering whether this is ultimately a more effective strategy if the goal is independence from Google's business model while offering a performant browser that works on all websites.
Mozilla has to put tremendous resources into implementing browser features that are uncontroversial and unrelated to Google's business model. And those resources are paid for by Google.
That said, there are certainly good arguments in favour of having more than one rendering engine. After all, privacy controversies are not the only reason why competition is healthy.
We already know the answer. Did those so called browsers, but actually Chrome mods, made independent decisions about AMP? Something they can't just change easily. The answer is no. And the same answer will be when Google will make Floc permanent and not switchable in Chrome. No need to test anything again.
With FloC, we now have a test case where we will see whether or not other Chromium based browsers can make independent decisions that go against Google's interests.