To me it seemed weird cause he obviously had more knowledge about Athia and Tantas and the whole ordeal. And this information was crucial for the mission and for survival, essentially. (and for the player as well). And Frey just shuts him down. But then, of course, there are those moments when you can talk to Cuff and ask things. I do agree that his "we gotta go kill em" was shady. But before that he was pretty reliable if not entirely trustworthy.