"If BUNDLE is in use and the a=cryptex attribute is present for a
media line, it MUST be present for all media lines belonging to the
same bundle group. This ensures that the encrypted MID header
extensions used to demux BUNDLE can be processed correctly. When
used with BUNDLE, this attribute is assigned to the TRANSPORT
category [RFC8859]."
First, as the usage of Cryptex is optional, why mandate it on all media lines? Could you explain the MID header processing justficiation?
Second, if mandated on all media lines, it will apply also to non-RTP media lines (e.g., a WebRTC data channel), and
then I think you need to have some explicit text about that.