listen, when you have to save the entire multiverse from some new omniscient alien extradimensional monster every week you learn to not give a fuck and enjoy the time you have at home. Whispy wood knows the routine and knows that he needs to make sure kirby is still up to battling if they want to stand a chance. consider it more of a spar so that kirby doesnt get rusty and kirby enjoys it because he knows its gonna be a while before he gets back home.