The point is that with open source you can effectively leech off of Google for now, while still retaining the flexibility to nope out and do your own thing at any point you decide.

Considering just how severely behind they are already (as I mentioned in my other comment, they’re often 3–5 years behind other browsers in implementing new web standards or operating system features), I see anything they can do to reduce how much they need to maintain independently as a good thing. In an ideal world where they had all the funding and development power they could want I might say sticking with the completely independent Firefox would be great. But that just isn’t where they’re at today.