Having been fortunate enough to get experience working in the QA department for a company that provides enterprise applications, I wouldn't think it'd be easy to detect a bug like this. It's unfortunate some in the general population focuses on the few bugs that make it out of a QA cycle than the [likely] hundreds/thousands that are fixed before the product is released. Especially an obscure bug such as this - who would think to write a test case to make sure a player's height doesn't change after a coach is fired? Why not make sure to have test cases to ensure players heights don't change after the All-Star game? After a star rated 86 and above is traded to a team with less than 40% win percentage? I remember people complaining about QA with 2K13 when that online shooting glitch occurred - forget the name of it, people would do some dribbling move outside the three point line and hit a high percentage of their shots - while that bug was even more obscure than this one, there were some people upset that it existed in the first place. But who would think to test for something crazy like that?
The game typically has far more content than most sports games out there. It's a wonder there aren't more significant issues that slip through the cracks I'd think. And I think that about a lot of applications, not just games. Probably the easiest way to get a better handle on things would be to offer less, so there are less variables to contend with. But guessing gamers wouldn't like that either.