I would propose to close this issue by saying that UDP is used.

There may be a case for using raw-IP for IPv4, if this is simpler for
interception purposes (RAO not supported in some places). However, it seems very
hard to justify using raw-IP without RAO for IPv6 (since this would require a
router to parse past all extension headers to find the protocol number). Having
defined the encapsulation as not meaningful for the rest of the specification
(see Issue 30), this would be easy to change in the future without impacting the
rest of the protocol.