PT spec: should 255 bytes be sent in the RFC 1929 UNAME field?

Section 3.5 of the PT spec says: If the encoded argument list is less than 255 bytes in length, the "PLEN" field must be set to "1" and the "PASSWD" field must contain a single NUL character.

When Kathy Brade and I implemented #29627 (moved), we viewed the above as a spec bug and allowed up to 255 bytes to be sent in the RFC 1929 UNAME field. Was that the wrong thing to do? Or should the PT spec be changed to read "If the encoded argument list is less than or equal to 255 bytes in length..."?