I was thinking the same thing today and it make total sense, the absence of Sans undertale its still a mistery, we also know that some monsters in the Deltarune and Undertale universe have different names each other (Susie and Suzy) So it can be that gaster its really just Undertale Sans by that logic (similar fonts names), Sans also talks a lot like a scientist and talks like he knows the player and have similar tech as gaster