Yep true.
I'd imagine it's only a matter of time till Intel are supporting it too. Honestly I still have no idea why nVidia made GSync given they are part of VESA and knew about the impending arrival of adaptive sync - they could easily have had their drivers all ready to go and avoided the bad PR of 'you can get what AMD offer from us too, but have to pay extra for it'.
Or, rather, as an interim solution I can see that it gave them a time advantage, but I've no idea why they don't also support adaptive sync - that would have been a win/win I feel. The GSync added cost wasn't so large that it's any different to any other early adopters tax so existing customers don't lose out. It would impose a maintenance cost though making sure that GSync keeps working as intended for a reasonable period while also supporting the standard.
Edit: To be clear, adaptive sync predates gsync significantly - on laptops. On desktops it may be that gsync was conceived before adaptive sync on desktop, hard to say, (and if so, and if it was this that triggered adaptive sync to come to desktop, then great! Well done nVidia, awesome idea) but certainly VESA were talking about it well before GSync became a reality. Perhaps nVidia had invested enough in GSync by that stage that they wanted to follow through. However they already knew about adaptive sync since the inception of the mobile version - and as they have mobile GPUs they should have been working on driver level support years ago. No idea if they have released a compatible driver on mobile or not yet, someone else can answer that if they know - I've got an nVidia m-series GPU but have no clue if it can support it, my panel can't so it's of no use to me :'(