Earlier quoted context omitted.
All Chromium "based" browsers are forks already -- how is this any different?
They’re less so forks than re-builds. They rely heavily on upstream and Google can certainly make it more difficult for them to maintain a “fork” that diverges too much from Chromium proper. Manifest V3 may be something they can easily keep out of their builds while maintaining the old method, but I’m no expert so I won’t comment on that. A fork implies maintaining most or all of the code base themselves, when in rea…
Microsoft is entirely able to maintain a fork of Chromium, or even their own proprietary browser.
What Microsoft has done is a cost/benefit calculation and decided that the benefit for maintaining their own stuff is not sufficient to justify the costs.
The thing about those types of analyses is that they are very company-dependent. That the C/B ratio is not good enough for Microsoft doesn't imply that it can't be good enough for other companies.