I think Sola is given a bit too much credit here, he shouldn't be seen as some miracle worker whereas San Millan is seen as a fraud (by some)
We know for a fact that Pogacar broke his wrist in LBL 2023 and had bad preparation for the Tour.
We know that he was much better in the classics of 2023 than before and we also know that he was, despite his bad prep, better than in the previous Tours. Some of you might say "but Pogacar didn't follow SM training and prepped for the Tour by himself", fair enough, that still doesn't explain his excellent classics campaign. So whatever it was that Sola was able to improve with his trainings, SM did something right