I agree, there is a difference. For instance, I think Giannis Antetokounmpo is a great athlete, but not necessarily a great basketball player. His understanding of the game is no where near his athleticism. However, LeBron is both a great athlete and player. To base your theory off that one clip is ridiculous.
I'm a die hard Celtics fan, and even I could see the referees were trying to fix game one in Golden State's favor. The Cavs were playing the best team in the league, who were also being helped by the refs, and the Cavaliers still had a chance to win at the end. To lose because one player couldn't make a free throw, another player didn't know the score, and your coach forgot to call a time out, just makes it that much worse. I couldn't imagine any competitor in that situation not being totally frustrated.
It just occurred to me, as to what you probably wanted LeBron to say. Maybe he should have walked back to the huddle and told everyone, "Good job, good effort" just like that kid in Miami.