Yeah, that´s one of the weird things about that subplot. Tremolo acts as if nothing would be happening.
It makes sense if he´s a "client" of the restaurant. He keeps the secret, for his own good. If not a client, my interpretation is that he can´t say something clear to Sage because he doesn´t have actually any evidence, only suspicions.
I think that at some point, Sage is going to know that Quinn is making a whorehouse of the fraternity, and Sage is going to go ballistic about that, being the president of the HOTs and responsible of the fraternity and all. Sage is going to confront Trmeolo about it, and there will be a HUGE difference between being a client or not. If Tremolo is not a client, he can say to Sage "I had my suspicions, but I have never told you because it was only that, suspicions, and I didn´t want to spoil your friendship with Quinn without evidences" and Sage will be OK with that. If Tremolo is a client... what is he going to tell Sage? Probably it doesn´t matter: Sage will consider him a traitor and despise him anyway.