See Roy jones at 175. Holding a good portion of the belts and being better than everyone in your division is being undisputed. Lineal is pretty much beating the man. For instance forrest beat Mosley and became lineal who got beat by mayorga and mayorga was considered lineal Champ, then spinks, Judah , etc.
The man who beat the man who beat the man. To start a new lineage, in theory the consensus #1 and #2 should have to square off. In the Klit era, #1 and #3 can be acceptable. Meaning I considered Wlad the man, personally, when he secured his KO win against Byrd in the rematch.