The "official" reason may be different than the actual. Watching her play tells me she is about hype not hoop.
Clearly sweating in the gym isn't about turning up the ambient air temp but about turning up and doing the hard work. Hard work can turn a mediocre player into a better player. Not overnight but certainly over time.
From videos released, it seems she already listens to and dances to hip hop. This isn't against hip hop. Her move to the hoop is severely lacking in control. Plenty of power but no finesse. Ballet offers both. I went to school with a young man that was interested in ballet. After years of practice, and at only 15 years of age while standing about 5'7", he was dunking. She needs the grace, poise, and muscle control that ballet offers. Those would greatly improve her performance.
I do not watch WNBA full games, but I've seen many highlights. Her shooting percentage within five feet of the hoop is atrocious. As a taller player, that should be her bread and butter. Lisa Leslie has worked with her with little improvement.