I don’t know all the details but I would think it was specific physical adaptation rather than a belief issue because the others in that group had thrived on S-to-L at that time. I think, though, if you look at both the approaches I’ve outlined, they are not nearly as severe as the type of pounding program you mention.
I would also mention a case I became involved in with a female 400mh. I had a number of discussions with the coach and wasn’t getting anywhere when I suggested that his program was impossibly hard.
When the girl moved here for school, I was asked to supervise technically, so, rather than argue fruitlessly, I simply discarded his plan and switched to a S-to-L plan and didn’t tell him since he wasn’t here to see it anyway. Her speed came up dramatically and she dropped 2 seconds in the 400h and made the Olympic team.
Only problem was, after not being told, the coach became more convinced than ever that he was right all along and he gained credibility because of her results.