Perhaps I am not getting what you are saying, but I think the statement by @Janhein is not quite accurate: I don’t think anyone made a comment that “modern training logic” (I assume that refers to the state-of-the-art as practiced by best-of-breed coaches) is supposedly obsolete and to be replaced by a black box algorithm that cannot be explained.
I think TR has distilled the state-of-the-art (as TR sees it at least) into its ML model. We can disagree whether TR actually did use the state-of-the-art or whether at present we have sufficient knowledge to implement what TR tries to implement.
And in principle the algorithm can of course be understood and explained — unless we start a philosophical discussion what “explained” or “understood” means. Since this TR’s secret sauce™, I don’t expect that they will share their knowledge or that many people will just be able to understand it. But in principle, I believe it can.
More important than that for users is, in my mind, whether AT’s recommendations can be understood by users. And in my experience at least, it has reacted exactly the way I would have expected to with a few exceptions. I haven’t explored the logic consistently or done an analysis like @Janhein , but all the adjustments went in the right direction.
The only issue I had with it was that it was too conservative at times and that it did not know how well I have slept (because at present it can’t). And even that was something I could understand given what AT is — TR has to work for a wide variety of athletes and erring on the side of caution makes sense.