I actually wonder how much of that decision was driven by Appel. For all his shortcomings as an ethical person, which are numerous to my thinking, Boras is pretty sharp - sharp enough to understand the dynamics of MLB's new draft system and that by going back to Stanford, even in another subpar draft class, Appel's leverage is severely diminished. Only thing I really see him gaining is more time to sign as a senior. I'll admit, though, having more time like that is an area where Boras thrives.
You may well be right, which would be a shame as I'm not as high on that kid as he is in himself (which generally is a good trait, but excessive ideas of personal value have brought down low many great people). I don't know enough about how a draft looks, particularly a year from now, but I do know that the arm can a frighteningly fragile thing. One misstep, even a freak accident, and the cliff of no payday happens.
He's also got the risk of really putting himself under a lot of self-induced pressure next season to perform at a high level. He may not handle that additional pressure well and could crater under its weight. There's not a real significant difference between first round first pick slot money (assuming that he gets picked there) a year from now and slot money for his pick which was money in the bank right now. I hope that it works out for him, but I'm fearful that it won't.