What does "Never Whistle While You're Pissing" mean besides the most literal interpretation? :-
It means that you should concentrate on one thing at a time, man. Whistling while you're pissing means that you're not concentrating fully on either: you're a robot, man.
But I thought you are the robot?
Just because you're the robot doesn't mean you're the robot. Did you even read the book?
There's a reference in the Appendices to Aldous Huxley's novel Island, in which the Rajah trains mynah birds to fly over the island saying "Concentrate!" and "Here and now!" to remind the people of the island to concentrate fully on the here and now. Huxley was a friend of Timothy Leary's. Leary was a friend of Wilson's. You do the math.