It is their original play. However I think this is just “Chrome is going to do this anyway and we’re not about to write custom code to work around it.”
The only other option is to keep v2 in chromium itself and have Chrome disable it... While still paying the cost of supporting it in all new feature dev.
There's no world where Microsoft spins up a new engineering team solely to deal with the extra cost of keeping v2 around.
That said this sucks. I got my first internship on the Internet Explorer team by talking about how hard it was to install an ad blocker in IE, compared to Chrome.
Modularity in SW is still a challenge after 50 years of progress.