Different between NoFap and Wet dreams?

Most people on the NoFap program are on it because they are addicted to PMO. For them, Wet Dreams are diffrent then PMO because it is just the body's natural reaction to too much stored up cum, not them actually watching porn or masturbating. They don't have a choice, it is just a perfectly natural bodily function. However, like you pointed out, it can still lead to a "drained" feeling. So, like you asked, what's the point?
The only thing I can really say is that the drained feeling you get from wet dreams is supposed to be not as bad as when you actually PMO. Also, wet dreams eventually stop after a while. Hope that helps, and good luck!