Good point about the rankings slip potential. As it stands, as has been said upwards in this thread, that MC, and most of clay, including RG is still in the balance, if he remains unvaccinated. Wimbledon, for now, looks like he can play. IW and Miami are very much in question, but the USO is too far off to say.
All who played the AO, yes, including those who were stated or implied to be "disinclined." (See below re: Adria Tour.) Tsitsipas had stated disinclination, I believe, but he did it.
I know we discussed on here immediately after the Adria Tour, how they blatantly ignored whatever protocols were being done in the limited number of exhibitions previous, at that time. I was of the opinion, and I still am, that they made strong choices against the protocols, because they (at least Novak,) had already told the USO that he was against their strict protocols for putting on the then-coming USO. I think Zverev was a fellow traveler on this, probably Dimitrov and Thiem, as Thiem and Zverev were still playing fast and loose with protocols after Adria. I know you didn't agree with me, Margaret, because you are kinder and less cynical than I am. But given what we know now, I have to think that Adria was staged as it was to prove the lack of necessity for strict protocols, and it back-fired on them. But Novak is stubborn, and he's standing his ground, to whatever extent, even though he wafts and waves over being firm in his beliefs, and just trying to get around things because he's rich and powerful.