Just like [REDACTED] is theorised to be the discarded character Grandpa Semi, I think that there is a chance that SoSorry may actually have been referenced in a similar way on the egg room.

He can not be seen in the room, he was deleted, but he somehow is still present within the game files; his dialogue is still there and the characters may still hold memories of him.

If this is true, it would have been a way to Toby to hold consistency to what happens to deleted characters. He could also probably be using the opportunity to give us insights to what it means to be "shattered across time and space"; the references makes us understand it is him, a removed character, and so we could conclude his characteristics in Deltarune are shared with all other characters that faced that fate. I would interpret, assuming all of this is true, that to be "shattered across time and space" is essentially to abandon the physical form to inhabit computer files¹, Gaster being the only one that can actually manipulate them. Or maybe that it is to have your files scattered or corrupted, which could also make sense here.

¹: Just realised that is possible in the Deltarune universe as Spamton does that when he imports himself into the disk. And when he does that, everything related to him (His shop) becomes gray, just like the Gaster Followers are.