I'd say in practice it doesn't really matter. For the sake of the argument let's assume that gorhill is wrong and the Google engineers really think this is the right technical decision, that's good for them but we still end up with subpar ad-blockers.
Of course these types of compromises crop up all the time when you're designing software, but then the problem is: if in the near future one Google engineer has an idea to improve the ad-blocking interface by, say, redesigning a certain component, would they do it? Would management let them do it?
There's a clear conflict of interest here, I expect ad-blocking to suffer death by a thousand cuts on Google's platform. Not necessarily because there's an evil master plan to kill it, but merely because every time there'll be a technical argument in favor of gimping it they're very likely to go with it while every time there'll be a proposal to improve it I'm sure there won't be a lot of motivation to implement it.
So even if we give Google the benefit of the doubt here I still believe that it's a huge problem and we can't let them effectively control the web. Beyond that in this particular case I'm not even sure I'm willing to give them the benefit of the doubt, the technical justification seems iffy to me (and the burden of proof is clearly in their camp) and there's been a clear pattern lately of Google moving to reduce the impact of ad-blocking (such as them bundling a minimal ad-blocking with chrome, most likely as an effort to dissuade people from looking for better third-party blockers).