Donald Carr writes:
At the link below, you can go to 19.1.6. It is a very strange ordering giving priority to two parameters that should be first, if present.
https://www.ietf.org/rfc/rfc3261.txt
19.1.6 Relating SIP URIs and tel URLs . . . .
To mitigate this problem, elements constructing telephone-subscriber fields to place in the userinfo part of a SIP or SIPS URI SHOULD fold any case-insensitive portion of telephone-subscriber to lower case, and order the telephone-subscriber parameters lexically by parameter name, excepting isdn-subaddress and post-dial, which occur first and in that order. (All components of a tel URL except for future- extension parameters are defined to be compared case-insensitive.)
OK, telephone world is very weird.
-- Juha