they can easily just blacklist ubo if they really wanted to remove it. And they can make it plausibly deniable - by blacklisting the extension id of anything that is in the chrome extension store that originally had manifestV2 (which will have some collateral damage, but obviously google doesn't care).
That's what the registry entry for the manifestV2 time extension is for - this was actually known for several years already, and 2025 june is meant to have been the deadline for that development.
