I don’t think Bundy is talking about run of the mill porn here.
Not to be adversarial here but..
Bundy was born in 1946. He claims to have gotten into Grandpa's porn collection.
In the 1950's, with no Internet, chat rooms, P2P networking, etc, the US postal service was the only way Grandpa would have been able to get his porn. And the postal service was watching for stuff like child porn and other bizarre stuff. So how would Bundy have been able to get his grubby little hands on non-run of the mill porn.
He couldn't. Th whole porn thing was a smoke screen. Bundy, and other killers like him, want attention. What got him attention - "Oh, porn made me do it."