I've rewatched some clips and I propose this:
We see Gene Takovic being trapped by doors closing on him in the trash compartment. (how's that for a metaphor) And after he waited on the floor we see him leaving but also a scratching on the wall
SG was here
That moment, beetwen when he sit on the floor is what we see in Better Call Saul. He is reminiscing on what lead him where he is now and what men he was. That's why he have the Saul age through series (with that haircut) and people he meet for the first time are the age he last remember them in.
Proof of theory:
When we see Jimmy McGuill showing his brother Chuck passed bar exam they are not younger. Chuck have the same gray hair and same haircut as when Jimmy see him for the last time. Also Jimmy look exactly the same (with haircut) apart from clothes for much younger, frivolous person. Clothes that are in, for me, clear constrast with ambulance chaser haircut.
Semiproof of theory: Is this is Saul memory how he know about things that happened without his presence? Because he was told about them by participants. That's why people complain that BCS Mike is much better/smarter person who shouldn't be shot in BB. But this is what Mike described himself to Saul. In BCS Mike is this almost super human comic book detective. It's because it's his stories and in such everyone like to paint themself better, smarter, with all the coolnes and strateg all layed out before acting on.
Another semiproof: There is a scene when Jimmy is sitting outside Chuck house who scold him. This is the same position he sits in that trash room. But during that scolding Jimmy is becoming Saul. And until one point it was Saul who was playing Gene. But when he stand up back again he might stand up as Gene. "SG WAS here"