This is formed from the famous quote, about Bielsa coming to his house, and, simply checking his calf muscles when he was in bed, as a young/youth player.
The reality is that, I think there is a very strong correlation to strong (or optimal) early muscle growth and organ development. As I have spoken about in many threads before (on other forums), it is no good a player like Edwards getting to 20-22 and hitting the protein shakes and gym. He will not have developed the bone mass, Kidneys or Liver function to support all the extra metabolic churn that will induce, so may get him in top shape 23-26 but then he will likely be the perpetually injured type (IMO using Edwards frame as an example).
This somewhat unskilled mindset of Pochettino, if real, is very helpful when looking at a players ability to potentially cope with high intensity roles, but lacks the understanding (or trust) of a sports scientist who can decide certain aspects in reporting to a Sporting Director, is my suspicion.
This Leeds lad, would be a key point, he may have the right frame, good technique, but do they know how it (frame) has been grown? Is there any real investigation into nutritional profiling and lifestyle, not sure at this level. He had a seizure, which given some other identifiers I see, would bring huge alarm bells about his Liver for me, and, whether he has the right mindset to adapt his lifestyle for Pochs needs.
Think there are some key areas, such as this point you raised well (or BC, whoever questioned the young lad coming in, contextually) that the club could really use a Sports Director for, but worry how it would mesh with Poch and Levy.