I think going back a few years I was all in favor of pitchers just developing over the summer at a facility like a DL, EC or Tread. Now I realize it's pitcher dependent.
As an example my freshman son pitched a little over 24IP, had 26K and a .230BAA with less than a hit per inning. BUT, he also had 26BB. He had the stuff/velo to get kids out, but really needs to work things out the mound. Indoor live ABS just aren't the same. Of course gaining velo is always great, but right now he needs to feel some pressure on the mound. He is trying to balance summer ball while also training remotely with Tread.
I know another kid. I don't know the exact number but walked maybe 5 batters in 30 innings. Started the year well, but once teams got a scouting report on him I think he finished with more than 2 hits and inning, and about a .400BAA, with balls breaking windshields in the parking lot. He was topping at 85 and couldn't land an off speed pitch for a strike so batters just sat FB. This kid would likely benefit from training all summer and increasing velo and stuff.