That was what I was told when I ordered my 2020 S as well. I think the advisors mostly know about the newer heavily sold models. The S and X have always had Sirius and FM available. The SiriusXM site shows that the 2021 Tesla S and X have the capability.
Vehicle Availability | SiriusXM
Check your vehicle for SiriusXM Radio. Many new and used vehicles come with SiriusXM. Find out if your car or truck includes SiriusXM and activate your radio subscription today.
www.siriusxm.com