Hi @runforrestrun,
Welcome to the Auth0 Community and thank you for your note.
You are right: the OIDC specs don’t include a definition of OIDC access token.
Actually, that term came from the reader I was replying to.
I used their own term to conclude that what they called “an OIDC access token is nothing but an OAuth2 access token”.
It’s even in your infographic. IMHO “OIDC access token” doesn’t make sense.
Where do you see this reference in the infographic? 
I can’t see it. It explicitly references to OIDC for the ID token and OAuth2 for the access token, as far as I can see.