if i hear that term for anyone who is a bjj blackbelt who wins a local tourney, i'm going to scream like a choir boy running from a priest
they are all one
A lot of them will have won the Mundials at lower grades and so call themselves a world champion.
Lots of weight classes. Several belt divisions. How many years has the Mundials been going on? Plus every other organization can have a "World Champion" too, in all those belt divisions and weight classes.
It's like having 'world' champions in all of the different boxing orgs and mma orgs.
Bah. IMO, to be a BJJ world champion, you need to have won the Mundials in your weight class at black belt or the Mundials black belt absolute, period. Everything else requires a rider (ie: Copa World Champion, or Master's World Champion at the Copas, or Purple Belt Absolute Mundial Champion, or ADCC World Champion, or Midwest Champion of the World).
Leaving out that rider is disingenuous, although common.