He expects the conversation to go on, to become something sprawling and complicated and laden with nineties frat boy lingo that leaves him baffled as to just why he likes (not likes, obviously, in the context Andy used it – just … likes) this person, but Andy stays quiet.

This is so bittersweet and in-character all around: how Andy makes the gradual switch from outgoing to somber and how Oscar has to assure himself mentally that he is not invested.

Semi-related: those spoilers are GLORIOUS.