Emby uses the id3v2.3 separator "/" for multiple artists with id3v2.4 tags
In id3v2.3 the separator for multiple artists is defined as the / character. Clearly this has some unintended consequences with artist names like AC/DC, G/Z/R or K/DA, but that is what it is.
In id3v2.4 the separator was changed to the null character.
However, Emby splits artists by / in both tag formats, so an artist like G/Z/R still gets split in three, even if it's an id3v2.4 tag.
the question may be moot, unless emby would consider moving away from ffprobe for music tag extraction.
https://superuser.com/questions/1282809/is-ffmpeg-able-to-read-multiple-values-in-an-id3v2-4-tag
i dont think ffprobe supports reading multiple values separated by id3v2.4 null character specification
i have just tested it again 3+ years on from when this bug was reported and as far as i can tell ffprobe is still deficient.
i used mp3tag to write an id3v2.4 multivalue artis