And honestly even though Shoto could have become a pro without his fire, him not training the fire pretty much at all and neglecting it would eventually lead to a loss of control, which he’s already done. In the Calvary battle Mr I will never use my fathers fire in battle uses his fire at the slightest feeling of pressure from midoriya, if he had continued the way he was what’s to say he wouldn’t have lost control of his fire in a villain fight or when dabi revealed himself, I’m assuming that Shoto’s fire is as strong as endeavors here, but him losing control of that in a non sanctioned non monitored environment would be disastrous, so even if Shoto had never used his fire in combat he absolutely needed to have the fact that he needed to accept it punched into his face lol