It would kill the headphone market (as it currently stands) if all manufacturers targeted the Harman Curve, because points of differentiation would be less. Besides, it's known that even in the Harman study that not everyone likes the bass level included in the Harman Curve, with a proportion of people preferring more bass or less bass - so there's still scope for manufacturers to offer different bass levels even if they were targeting the Harman Curve generally - but still I think headphone companies don't want to tie themselves down to that because again it's decreasing points of differentiation, and hence unique saleability. Personally I think the over ear Harman Curve 2018 is about as good as it gets currently, but I don't see all headphone manufacturers doggedly following it. The good thing is we have Parametric EQ, so it's not a problem! (Myself, I quite enjoy the necessary EQ journeys!)
I agree. If you have only one headphone, get one that follows Harmon. If you enjoy having a few different ones, then you don't want them to all follow Harmon.
BTW, the Ether Flow 1.1 predates Harmon 2018.