I do several seeding meetings a year. I think there are misconceptions with this rule. The problem is solved with 2 questions before every weight.

1. Does any winning record not want seeded?
2. Has any losing record beat anybody in the bracket with a winning record?
Those questions almost eliminate coaches trying to place kids on the bracket.

A person with a losing record becomes seedable if they have beaten somebody in the bracket with a winning record. That meets, “common opponent”, criteria.
Example. Sam is 13-2, Sam lost to Jon who is 13-15. Jon, therefore has earned a seed on the bracket. That seed may or may not be higher than Sam’s, dependent on others criteria in the bracket. But Jon is in the seedable conversation.

Example 2
Mike, 12-20, beats Jon 13-15. Mike is not seedable because he has not beaten anybody in the weight with a winning record.

We seeded 12 deep at regional. I don’t see a reason to seed more than that. That seeding debate most likely would not have a definitive solution. Seeding more would allow savvy coaches to “place”, kids on the bracket. Neither of those are healthy for a seeding meeting or my old ticker!