No one is arguing that this wasn't the world championship. The moniker SB wasn't officially used for a few years.
The origins of the Super Bowl
The Super Bowl wasn’t originally called the Super Bowl. At least not officially. The first American Football League-National Football League Championship Game was held in Los Angeles on January 15, 1967.
The 1967 title game was the first held between NFL and AFL teams, as the two leagues merged the summer prior, with an agreement to play a championship game at the end of each season. Commissioner Pete Rozelle settled on the cumbersome title after league owners were unable to come up with anything better.
This, from football historian Harvey Frommer, for Time in 2016:
One of Rozelle’s suggestions for the name of the new game was “The Big One.” That name never caught on. “Pro Bowl,” was another Rozelle idea. Had the name been adopted, there would have been confusion, for that was the name used for the NFL’s All Star game. “World Series of Football” died quickly, deemed too imitative of baseball’s Fall Classic.
Frommer wrote that Rozelle settled on the ‘AFL-NFL World Championship Game,’ but as you can see in the Super Bowl logo graphic above, the logo for the first title game was actually just the words, “First World Championship Game AFL vs NFL.” That’s certainly not as catchy as…anything else they could have possibly picked.
As for the term Super Bowl, credit goes to AFL founder and Kansas City Chiefs owner Lamar Hunt.
As his son, Lamar Hunt Jr., explained, the idea came from his “Super Ball” toy.
My dad was in an owner’s meeting. They were trying to figure out what to call the last game, the championship game. I don’t know if he had the ball with him as some reports suggest. My dad said, Well, we need to come up with a name, something like the ‘Super Bowl.’” And then he said, “Actually, that’s not a very good name. We can come up with something better.” But “Super Bowl” stuck in the media and word of mouth.
Dig a little deeper and you’ll find some questions regarding the origin story of the game’s name. In January of 2015,
The Christian Science Monitor published a story about how the Super Bowl got its name, crediting Hunt, but calling into question when the game officially took on the name Super Bowl.
Although “Super Bowl” was used unofficially by fans and the media alike, the term was not officially adopted until the fourth annual championship in 1970 – the year before the now famous roman numerals were attached. In prior years the championship game was officially called the AFL-NFL Championships or World Football Championships.
Over the years, people challenged the name, and others have questioned the legitimacy of Hunt’s role in coining the term.
In 1969, there was a contest to rebrand the game under a more sophisticated name. “Ultimate Bowl” and “Premier Bowl” were the most well received of the many suggestions, but neither stuck and the championship game has been officially called the Super Bowl ever since.
An SB Nation post three days later regurgitated that point, reaffirming the stance that the game wasn’t officially called the Super Bowl officially until the fourth iteration. But the logos above and this photo from the first Super Bowl below seem to indicate the name was more than just a passing comment in an owners meeting that took off with the media for four years before the NFL adopted the term.
https://billypenn.com/2018/01/24/how-did-the-super-bowl-get-its-name/