Why? It's a fan made mod, that's the worst example you can use.
Why? Because you say it is? Why is the fact that it's a fan made mod relevant?
For a new fighting game to reach its maximum potential it has to be played as a major focus starting out. It's not exactly healthy that the first tournament Smash 4 is entered in it's treated as a side game. That's sending a message to the new players that the game they just bought is second rate and they are more likely to quit early in the game's life span. A game being a side game attracts less entrants and exposure... EVO has proven this already.
I feel that you have to assume a game is solid until proven otherwise. Your method is more towards a game is mediocre until proven otherwise.
Semantics. It won't really be a "side-game", tucked away in some corner someplace like Fist of the North Star at EVO. A lot of this shit is perception and how TOs market the event. Smash 4 can be a huge draw to an event, but people still look forward most to seeing Melee grand finals at the apex of the tournament until Smash WiiU proves to be more competitively interesting at that point.