Thanks Rob, yea we have that set. I was just reading the TechZone link here.
But I wonder if article is incorrect or perhaps for a different use case? Maybe they can for more context around it? IDK.
"When using Citrix Gateway, configure StoreFront with the details of the Citrix Gateway and Callback URL, because logon evidence is transmitted via the Callback. Configuring Logon type as "Smart card" helps native clients perform SAML authentication. The setting "Fully delegate credential validation to Gateway" enables the StoreFront servers to delegate user authentication to the Gateway, which allows pass-through SAML authentication from the Citrix Gateway. IT admin has created the FAS Group Policy Object that containing the trusted FAS servers list and applied to the OU where the FAS Servers, VDAs, and StoreFront Servers reside in the AD domain."
https://community.citrix.com/tech-zone/design/reference-architectures/federated-authentication-service