why is EUI-64 encoded as DNS-ID

[mcr]

If the EUI-64 format is used to identify the subject of an end entity
certificate, it MUST be encoded in a subjectAltName of type DNS-ID as a string
of the form `HH-HH-HH-HH-HH-HH-HH-HH` where 'H' is one of the symbols '0'-'9'
or 'A'-'F'.

this seems really odd. I was looking for a SN, or SAN that would encode EUI64, and I feel surprised not to find one.