Arjuna is being precise here. He tells Krishna: I have heard from you, in detail, how all beings come into existence and how they dissolve back. And beyond that, I have heard of your imperishable glory. He calls Krishna 'Kamalapatraksha' — the one whose eyes are like lotus petals. It is an address full of tenderness.
There is a reason Arjuna recounts what he has already learned before making his next request. He is not repeating himself out of habit. He is showing Krishna that the teaching has landed. Like a student summarizing the lesson before asking the next question, Arjuna builds his case with honesty and gratitude.
The word 'avyayam' — imperishable — stands out. Among all the things Arjuna heard about, it is Krishna's undying glory that struck him deepest. Everything else in creation comes and goes. Krishna's greatness does not.