I made this importance: 'very high' contact a priority contact, then returned him to normal contact a day after (kanta's den --> nova maxios --> tibicena). He still gave me the missions he would've as a priority contact, which made me think it was weird. opened up intel tab (while in colony menu), and saw he wasn't. when i went back to his contact page, his missions changed.
I tried replicating it, and managed to by toggling 'priority contact' in-menu. Maybe I remembered wrong...
Also, I've noticed that making a contact a priority contact sometimes reduces the amount of missions? Intended?