Per the WS-SP 1.2 spec, section 5.4.2, "This required element contains elements which MUST be copied into the wst:SecondaryParameters of the RST request sent to the specified issuer. Note: the initiator is not required to understand the contents of this element."
The STS client copies these values directly into the body of the wst:RequestSecurityToken element in the request to the STS.
So this policy:
Becomes this request:
WS-Trust 1.0 and WS-SP 1.0 do not support the wst:SecondaryParameters element so backwards compatibility should be retained per the interopfest samples.