The category has the same start and end requirements as Story Mode Singles, with the added restriction that your character may not have their starting stats adjusted in any way. This means that all level-ups must go to your AI partner, no custom clubs, and no special items.

(And my recent singles run would be the first run of that board)

Those of us who talked about it in the discord server lean towards only singles having a low% even though my submitted all tourneys run sort of counts as a low%