Trump is pretending now to be pro-vaccine, and owning it, claiming it, because he has more chance to motivate THE SHEEP to be wary of it doing that, than he does to lose reputation with anyone who works this out for themselves. Trump is offering himself up for sacrifice in a sense because he is willing to help attract criticism of the vaccine. Those who disagree with Trump's pretended position are against the vaccine will not take it and not be at risk from it for now. But those who might question the vaccine could be put-off if it meant "agreeing with Trump" so Trump cannot be antivax openly.
There is even the chance some will stay away just because he pretends to like it. Kamala even said - "If the vaccine has anything to do with Trump, I ain't taking it"
I think you're right on, but most importantly, he made it clear that it should be an individual choice. That's all we need to hear. We never needed a president to tell us how to think. We needed a president who allowed us to think for ourselves. His pro-vaccine statements used to bug me until I realized that his supporters are able to still support him and still make up their own mind.