I generally agree with this but we've all seen games where a WR runs half-hearted routes or such. Or a team just looks like 11 guys thrown together. I think that's generally what they are suggesting. In the Giants game, the interim HC ordered the team to go for it inside the ten on 4th and five instead of taking the FG. I think that was a bit of not caring if they won the game and giving Dart an opportunity inside the 10, for instance. If they needed that win, they would have taken the points. But straight tanking, like actively trying to lose, I don't think that happens much, certainly not team wide. That was one of the things exposed in the Flores allegations against Miami and the only thing that the commissioner came down hard on Miami's owner for was suggesting that the HC lose on purpose and offering him money to do so.
But if I'm Packers' QB Tune, I'm thinking I can show teams I'm more than a practice squad guy. I'm gonna try my darnedest to win. Ditto with any backup getting playing time or any potential free agent. Plus there is pride in a rivalry game.