And not the first time it's happened, either. I've seen at least one person defending it on Reddit ("It's only 30 seconds!"), but to me that's ignoring the bigger issue. Not only does the time add up, it's the principle of the thing. As you said, it's another F2P mechanic in a AAA game.
Sure, they play it during loading when you wouldn't be playing the game anyways but like you said it's the principle of the matter. I actually didn't mind the 2k TV videos that occasionally have you opportunities to earn a little VC
The other thing is that while a game is loading, you can normally edit lineups and such in Play Now or MyLEAGUE, but not while there's an unskippable ad playing. To that end, it does have some impact on the experience. If nothing else, it's intrusive in a game that's already full price and has recurrent revenue mechanics. As someone mentioned on Reddit, it's also been done after all of the major outlets have reviewed the game, and not many of them are going to issue a revised review that criticises the practice.
That was smart to not have it in the original game but to add it after the reviews are released. 2k feels like a slimey politician who wants to do whatever he wants and breaks the rules for his own gain