This. It's extremely expensive to keep core functionality like this in a fork. Every single surface that manifest v2 touches (js runtime, extension hosting, permissions, network, APIs, chrome even) that gets changed upstream has to be redone to account for v2. Every new system built into Chrome that only works with v3 has to be effectively back ported to v2.

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.