The document makes heavy use of EDHOC and states that C509 might be use as an optimization. Other parts of the draft seems 100% ASN.1. EDHOC makes heavy use of CWT/CSS/C509. It would make sense to be able to request the server to issue C509 certificates. Currently that does not seem to be possible.
From John Mattsson's review (https://mailarchive.ietf.org/arch/msg/ace/h85KdNLkMxqzCZjJlY-fGlPEyVw/):