Most people would.Of course I am more than happy if a watch runs +1 sec/day on my wrist but I would not call it to run within COSC specs.
I think you're taking things too literally. I don't think it's unusual to talk about the primary timing variation (+6/-4) as "COSC specs". It's a commonly referred to short hand, and should not serve as a stand-in for "meets every letter and test of the entire COSC standard". If you look at the context in which Archer was using it, I think that's pretty clear. All he was saying is that he can get many movements to run with that daily rate variation.
So YES, when a watch runs within the daily rate many, many people refer to that as running within COSC specs. Would it pass the actually COSC testing? Maybe, maybe not, but that's not what is being referred to. I'm not sure why it would