I will say, I remember one year kobe came in completely jacked (at about the same age) but he didn't keep it long term for whatever reason.
Based on the amount of energy being exerted by an elite wing for (ideally) about 100 games a year, it seems incredibly difficult to carry a lot more weight than is "natural."
Even in my rinky-dink college athlete days we used to lose about 10 pounds over the course of a season.
Tatum has the benefit of naturally filling out and getting stronger until he's in his late 20's, so hopefully whatever turns out to be "natural" for him is big. I know his dad is gigantic.