Endurance running is pretty useless for baseball. It doesn't hurt to do it but I don't think cc or miggy run a good mile and they play mlb, baseball is about explosiveness, not fitness.
Maybe the coach wants to test for willpower to train for it and fight through it.
Personally I think a bit of aerobic training is not bad for athletes because it improves ability to recover and withstand hard training. Shouldn't be the main focus of training but a little can't hurt.
To really improve in baseball jumping and sprinting helps a lot more but a bit of aerobic training won't hurt you either as it is a myth that endurance running makes you slow (several world class endurance runners could go the 100 in under 11s), it just doesn't make you fast.