I think the difference is mostly theoretical. Consider the proposed extension changes: no one seems to like them, but Google will be able to push them through anyways. Maintaining a Chromium fork is a huge undertaking that only a few companies would be willing to invest in.
Maintaining a fork is much less of an undertaking, than reimplementing all Chromium quirks. Hence plenty of Chromium forks exist, but only one last barely competing browser.
I don't think Opera, Vivaldi, Brave, Yandex browser are trivial by any measure. Heck, even something small and independent, like ungoogled-chromium, is in no way trivial.
