He has to be shitty at Chess because he ducks out any attempt to get him to play it. If he had any skill, he'd be broadcasting it just like his shitty Super Turbo streams.
Even after being told there was a free chess game on PS4 he could download in under ten minutes, he still said "I don't think that's something people would want to see!" Which means he knows people would love to watch him fail miserably at it.
He's making up bullshit he thinks no one could ever debunk because it's been so long. Who the fuck is going to track down his old Chess Club teacher to prove he really sucked? Nah, tell tall tales and make up reasons why he can never play Chess in front of other humans ever again instead. That'll throw us off the trail.