I think this goes for a lot of young players. Tatum is 23 - if it's true, it shouldn't come as a major surprise. But I don't think it's totally true. Rather than not caring about winning, I think he has just gotten accustomed to winning and being a star while doing it. This obviously started his rookie year when he helped lead the Cs to game 7 of the ECF.
After the end of last year and the beginning of this year, I think Tatum is beginning to reassess how difficult it actually is to win and is finally taking measures to not necessarily make it all about him. Besides, the quote below is kind-of stupid. With most young players, you hear that they would rather score 40 and lose than score 15 and win. Nowhere here does it say Tatum is okay with losing...and that is a good thing for his age.