In the link he posted its outright stated that more and more will come with time.
We'll make more things compatible over time, bit by bit, but they won't be compatible at launch.
Also we did get headgear since the release of shadowbringer that work for the new races.
Yes, which in turn would be great for everyone since it would mean more rewards than just helmets that most of the people will just put away because the just look horrible for a lot of us anyways.
If you go around and limit something then you need to give those people something in exchange. Otherwise they are paying the exact amount of money as others but will get less for it. And seeing how their sub numbers is over a million with shadowbringers they will surely have the money to create a bit more than those few things for an event.
(But I am also of the opinion that a lot of their events are bad..)
