What is gained by Nick's absence from the reunion between Gatsby and Daisy (page.95)?

Gatsby and Daisy are very uncomfortable at their reunion. Gatsby is falling over himself trying to impress her and acting like he's a kid..... rude and insensitive. Daisy is embarrassed. When Nick leaves them alone they seem to be able to smooth out their nerves and share their lives. We are not apprised of what happened after Nick left, only told that after he returned, "They were sitting at either end of the couch, looking at each other as if some question had been asked, or was in the air, and every vestige of embarrassment was gone. Daisy’s face was smeared with tears, and when I came in she jumped up and began wiping at it with her handkerchief before a mirror. But there was a change in Gatsby that was simply confounding. He literally glowed."