The main part of the browser is its main developer. In this case it is Google. If Google decides to add QUIC support to the browser it will appear in all of the clones too, because they are not standalone. If Google decides to move to the Manifest V3 then all closes will move to it too. Whatever Google decides to implement deep in the Chrome browser, other will have no choice but to accept.
As soon as will see even a single real fork of the Chrome, I will of course call it a separate browser. Just like I called Safari if you saw above. Safari and Chrome grow from the same source years ago, but Apple decided to make a real own browser, not just tune some settings and add or remove plugins.
Well, it's the other way around, actually. Safari's WebKit was based on Konqueror's KHTML, and Chrome's Blink was in turn based on WebKit. See here [0], it's pretty interesting
