"He never wanted me to be trained," Anakin says as he twists out of the way of her blade before using the spin to add more power to a swing of his own. "But you're not wrong."

Which might be the only reason Mace actually ended up relenting on the subject of his training. Once he'd become aware of his ability with the Force, there was no telling what he would have gotten up to without formal training. Which could have been far more disastrous.

Especially if Palpatine had gotten his hands on him then.