I can recall a situation in the mid-1990s in Southern California where the proverb was used to castigate a pair of co-workers whose relationship was causing problems at work. In other words, it’s not an interpretation I’m pushing, it’s one I have observed. It doesn’t have to be the original one, the main one, or the only one, just one that’s out there.
Yes, over here, “Don’t piss in your pool” is always used to admonish someone not to sleep with (A) the maid and (B) the employees. I’ve not heard it used for any other situation.