My 2017 kid is also playing basketball right and will be until the first week of baseball practice is done. (the good news, I guess, is that the hoops team has zero chance of making playoffs this year).
My thought has been that going to school and playing basketball is a pretty heavy load, so anything else he does has to come from him and not be pushed onto him. Also I think that in general basketball offers plenty of conditioning and exercise and that baseball work should be pretty minimal up to now. Over the winter break and when he has time and energy on weekends he continues to lift on his own, and he always does his band work, which for me is a health issue, so it's the only thing I allow myself to nag him for. He stopped throwing after fallball and cut down his hitting to one day per week. Now that we're about a month out from baseball, I have nudged him to start throwing with another basketball-baseball teammate 3-4 times a week, and also pitch to each other in the school cage when the get a chance, which will probably be 2 times per week. He'll also continue to hit off a machine once per week, and he'll hit a few times with an instructor if he wants.