I would not assume that to be the case. Many of the "fully open" hotels still have limited dining options open. Grand Floridian has been "fully open" for months and still only has GF Cafe and Narcoosees for TS--1900 PF, Citricos, and V&A are all still closed. Yacht club just has Ale & Compass: Yachtsman is closed.
O'hana was incredibly popular when it was open, and not just among Poly guests. I expect if it opened last July, it would have been consistently selling out at 60 days. I suspect its closed is less due to lack of demand due to the hotel side of Poly being closed, and more due to the fact that Disney does not want to cause transportation backlogs (boat/monorail), and crowding in indoor hotel lobbies, by opening incredibly popular restaurants near 10-K. Which is why I suspect Chef Mickeys is not open for dinner.