The problem with S.A.Y.S. for me is that it felt like a wasted premise. The central conflict would've been far more interesting if Spike were his usual helpful self conflicting with the headstrong, prideful Applejack. With the route they took, Applejack undoubtedly had the bigger beef and you just wished Spike would cut it out already.
And after watching Games Ponies Play, I can kind of understand why Spike wasn't invited. He would've been a third wheel. It seemed the Mane 6 had the welcoming routine planned out for awhile amongst themselves. I know RD said at the end "too bad Spike couldn't come, he would've had fun", but I don't see what real use he would've been this time. Despite the nobility of his actions, there really aren't that many transferable skills between saving an empire from the apocalypse and welcoming a games inspector. I'm sure when they do an episode about the actual games next year Spike will definitely be there.