Well, obviously the speed of gaining experience isn't a bug. Regardless, it's pretty obvious that the LeBron James of the above example does not correspond at all to the experience model of BuzzerBeater. There are many pro-league level players with more than 5 seasons as starters and playoff experience who are not even close to legendary experience. I don't think BB-Forrest's comment should be taken in the way that a few seasons and playoff appearances will result in very high levels of experience in BuzzerBeater, but more in the way that James can be considered an experienced player in real life even though he is a pretty young man (even in world of sports). Obviously he's a top player and a leader, so he must have some experience.
I believe the reason LeBron's skills and experience look the way they do is that these sort of distributions led to most realistic results (i.e., most like real life results of the teams) with the game engine in its past state. The skill/experience distribution would probably be somewhat different today, since the game engine has been updated. But I think LeBron would still have a very high experience, higher than what we see for example on many national team players in BuzzerBeater.
It seems the range of experience used in BuzzerBeater is fairly limited or at least a fairly large group of players stay at low levels. Anyway, if we want to have such discussions, we must use other forums. As far as we know, there is no reason to suspect a bug here. I'll close this, but feel free to open the discussion again (just not here).