It’s a fun joke the show tweeted out. But people actually believe that it is true. Yes, in the 2005 episode “Bonfire of the Manatees,” Homer was watching a game between the Seattle Seahawks and Denver Broncos. However, that is it. Nowhere in the episode did they predict that it was a Super Bowl. If you actually watch the episode, or read the script, they stated that the game was played at the Broncos’ home stadium. Also, Homer bet on another game later in the episode.
But people decided to run with it as if it was real.