AVCD is/was a common format used in Hong Kong which combines video tracks and audio tracks on a single session.  Some discussions:

1. https://hydrogenaud.io/index.php?topic=42728.0
2. https://cdrfaq.org/faq03.html#S3-16-3

It should be possible to attach a Disc ID to AVCD, as all of the tracks after the first couple are CDDA tracks that can be played by any CD player.  If so, it is necessary for it to exist separately from VCD.

And since AVCD can contain video tracks, it should also exist separately from Mixed Mode CD to be compatible with MusicBrainz Reports.  That said, I'm not sure if attaching a Disc ID to an AVCD would result in wrong track lengths for the video tracks.  From a Style perspective, it might be necessary to mark all of the video tracks as "data track" for the Disc ID, then shift the actual video recordings with the correct lengths into the Enhanced CD Data Track section.

Currently, these releases have been incorrectly entered into MusicBrainz as Enhanced CDs (to allow Disc ID, but shows up in the mediums that shouldn't have videos report) or VCD (which blocks the ability to attach Disc ID when there are CDDA tracks).