Rob,
Which part of the word "secure service option" in the requirements for service providers in the official PCI-DSS 3.2 spec, Requirement A2.3 is unclear to you?
What you allege would need wording such as "secure-only service mandate" -- which clearly is *NOT* what the PCI-DSS spec says.
Btw. this discussion is about the TLS_FALLBACK_SCSV, which is completely irrelevant in the face of PCI-DSS discussions, because it is clearly impermissible for a PCI-DSS compliant client to perform a TLS protocol version downgrade dance at all, so this signaling cipher suite can *NOT* be used (and will never appear) in any PCI-DSS compliant communication.
-Martin