Earlier I made a point to check to see if anyone here knew why presidents and their doctors haven't ever been bound to sharing their medical information with the public. The answer is pretty simple. So presidents aren't discouraged from seeking out medical attention for either physical or mental health reasons, due to the unfair stigmatisation of those with disabilities or just weird views on who can or can't serve in the oval office based on genetic information.
This is why FDR made attempts to conceal the fact that he was paralysed from the waist down. He literally didn't trust the electorate to have any faith in a man in a wheelchair.
In Bidens case, the lack of transparency could very well be to hide some aspect of his health data with the public that most reasonable people wouldn't see as something that makes someone unfit for office, like a past history with depression that isn't current, however, a past history of depression is the sort of ammo any political opponent would use and some voters would believe this makes someone unfit to be president.
So this is why the presidents expectation of privacy in regards to medical data is left intact. It wouldn't do for a president to be discouraged from seeking medical aid for both simple and complex issues. You really have to put yourself in the mind of different types of voters to see why this is the case. "Oh the president has boils on his rear? No person chosen by god to lead would have boils on their rear. You've lost my vote." Or "Oh I see Biden suffered from a bout of depressipn 40 years ago, what if he gets depressed again and kills himself while in office? Can't vote for him."
So there are lots of reasons why a president might not disclose their medical info really. From benign to serious. Hell there is even an incentive not to give out allergy information to not give any workable info to would be presidential assassins.
Fortunately, the physician to the president is required to give general health updates to the VP and the cabinet if they are at all concerned. This is why I'm of the opinion that if the democrats want to sensibly and reasonably practice caution, they should leave this in the hands of the VP and Bidens cabinet. The way I see it, if Biden wasn't fit to run, he wouldn't be fit to finish out his term either. If the unfair pressure gets too much and he decides to bow out; I think the best way to make that strategy work, would be to give Harris the reins, make it her ticket, (she is polling better now that people are more seriously considering this scenario, to their own probable detriment) and pick whomever the next best polling willing Democrat is, for VP.
That to me is just a hypothetical. I still think ditching biden is shooting themselves in the foot and nobody has proved beyond a reasonable doubt that Biden isn't fit for office because the office is still running just fine.