The only "you didn't work, so don't sprint" situation which I would consider valid is where you contribute to the best of your ability for a while, but get to the point where you can only hang on and the other riders extend the courtesy of riding at an even tempo in order to keep you hooked up rather than dropping you. If this is done in an effort to tow you to the finish with the break instead of being swept up by the pack as a reward for your contributions, then I would agree that it's faux pas to sprint at the end, even if you do manage to pick up a second wind during all the rest time.
If you find yourself in the "I can't work anymore, I'm just trying to hang on" situation, it might be wise to verbally concede the sprint to the other riders in hopes of not being attacked and dropped in your moment of weakness. Last place in the break is still better than falling back to the pack.
If you find yourself in the "I can't work anymore, I'm just trying to hang on" situation, it might be wise to verbally concede the sprint to the other riders in hopes of not being attacked and dropped in your moment of weakness. Last place in the break is still better than falling back to the pack.