Today I was in a simulator on runway 20R at KSNA. ATC gave me a VFR clearance and told me to fly heading 080 on departure. The runway has right traffic. I turned right and was told by ATC I should have turned left because you're supposed to always take the shortest turn to assigned heading when given a heading, even if the runway has an opposite traffic pattern.
My question is: Where does the FAR/AIM specify this rule? Are there any other legal publications that specify this?
Bonus points if you can cite a reference to this rule in any PPL textbook e.g. Jeppesen's Guided Flight Discovery Private Pilot. Thanks.