I don't think this is the case.

Having worked on Chromium, the codebase is very modular and internal API's change pretty slowly.

I can stop work on my project (which does fairly serious surgery to the internals of the rendering system) and come back a month later and typically spend less than a day to merge head back in.

Maybe things have stabilized a bit?

I worked on multiple projects modifying Chromium and V8 a decade ago, and the GP matches my experience exactly. Absolute mountains of dev time just tracking the latest release and what we wanted to do wasn’t limited to one module or subsystem.