Do you agree that the best employees end up getting put on the worst clients?

Someone in /r/accounting posted an interesting opinion:

The other huge loophole in the system is that the better work you do – the worse clients you will be put on as at the end of the day – they need someone really good to come get this hard shit done so they pull the best workers. Its a flat promotional scale so the key is to do mediocre work at a slow rate with a phenomenal attitude.

Is it actually better to intentionally be a mediocre employee so you don't get put on the worst clients?