So basically, they are meaningless?
What you are referring to in the business world contemplates an ongoing negotiation. Nothing like that exists here.
This is a promise, apparently subject to a contingency that it is good unless and until things change for the applicant, which is really not a promise at all. How loud would the howls be if As were only binding until schools found better candidates, willing to pay more money? (It was an A when it was issued at that snapshot in time with the current level of understanding between the parties, but then someone came along with a better MCAT score and a greater willingness to pay full price. Sorry. Please forgive us. We didn't mean to be disingenuous.

)
At this point, it honestly (pun intended!
🙂) does not matter. It's a shame for the candidates who need it to, but it doesn't. Schools know they are BS, and treat them accordingly, at least according to every single adcom who has posted on the subject.
It's actually kind of funny that so many people have not received that memo, and continue to sweat the ethics of sending them and then reneging on them. Adcoms are not as unsophisticated or stupid as we seem to want to think they are. People confuse causation and correlation when they send them and later receive an A. For everyone who has that experience, scores of people send them with no result. And then, of course, there are the folks who renege and then post about it to wind us up. Which we cannot help but oblige.
😎