No offense friend, but since you've only used humalog after training, your experience with insulin is crawling. I have been using insulin for about 11-12 years and I have tried everything, starting with insulin only after training, R humulin 2-3 times a day, humalog with every meal, before and during training, various combinations of lanthus and short insulin, and I am still careful that I don't know much about it.
I will give you one simple example why the use of humalog before training is beneficial - first of all, insulin will cause ATP to recover faster after the set is finished, so it will automatically translate into the best training and, consequently, a greater training stimulus for growth. The second thing, regeneration does not start after training, but only when you cause muscle damage. It doesn't work like that - "the body - hmm, this set was very hard, it caused a lot of damage to my muscles, but I will not start repair them yet, because the owner of this body still has an hour of training, so I'll wait" lol