I was reading through all the rankings in boxing and it appears that there is a possibility that we might be given one of the greatest superfights on 2023 if the promoters can work together. This is Naoya Inoue vs. Stephen Fulton as undisputed champion vs. undisputed champion which has never occurred before in the sport of boxing.
I don't think it's correct to call undisputed champion vs undisputed champion because they're on different weight, Inoue will become a challenger if he move to next weight on super bantamweight division since he doesn't have any belts on that weight and he wouldn't lost anything if he lose.
However Inoue should learn even though he's the best on bantamweight division, he may not become the best on super bantamweight division.
Agreed, however, technically if they win all the championships in their weight divisions, this would make them both undisputed champions. I reckon 2 undisputed champions in their weight division have never occurred in the past before which might make this the first time 2 undisputed champions will have a fight in the ring. This is will be very exciting for the fans hehe.