I would also add that for a developing athlete, short to long has its positives. However, one of the negatives is limited repetitions. I found in the 6 wk GPP my runners learned to “relax” when running, where I found them constantly tight doing s-l work prior. After the GPP, I think a good part of the success I had was their ability to run relaxed.
Also, I recall a conversation with Charlie and his point was along the lines of what we did in the end was a product of what came before. Remember, there were many years Charlie’s athletes did Long to short style training. Those longer runs do teach relaxation and build capacity in their own way, as does KK GPP.
Would Ben have done as well on S to L without those years of longer work? I don’t know the answer. Is doing long ot short and then going to short to long over several years the way to go? I don’t know either. But it is worth investigating…