Actually it’s not totally ‘accurate’.
All “National Leagues” award trophies to the winning team at the end of every season and have different names for those trophies, usually named after a sports person, such as a founder of a professional league, a coach, a player of iconic stature. Top of my head, NFL winners awarded Vince Lombardi Trophy, the legendary coach of GB Packers, for instance.
The only professional sport where the “world” title officially involved is the “The World Series” of Major League Baseball. The semi-finals are officially called World Series, iirc.
That said, it is also true that it’s the unofficial usage of the nomenclature by public that brings the word “world” into the picture.
The pundits, fans, franchise owners and officials of the respective professional sports boast the title “world champions” generously
I personally agree with you and find it ridiculous.