Perhaps since Goku and Vegeta did save energy until they faces Hit. Goku did tells Hit being a SSJB uses a lot of energy. If I remember correctly, Piccolo mention a SSJ (Goku) might not be able to harm Botamo.
I thought of it as pouring water to a cup, but the cup have a small piece missing in the bottom. If you keep pouring water to the cup, it will overflow. If Goku keeps attacking Botamo, his technique will overheat and no longer work until it goes down like a thermometer.