This is a scene in the storyline in which you save Wyatt. Later on, in the underground bunker where you crash with the resistance, you can use his workbench to craft armor upgrades.
After rescuing Set and returning to the base, if you try to craft an armor upgrade his guitar will be on the bench, and you'll see this cut-scene once you interact with. It's hardly an Easter egg as it's necessary to upgrading your armor at the workbench, and isn't well-hidden or hard to find.
