You're blind. You're deaf. Or rather, you just see what you want to see, hear what you want to hear. If you paid any attention to the post-match interview, you would've heard the man himself say his first choice was Amoonguss (the same as any smart and reasonable Pokémon player, at least in the absence of Togekiss), and only tried Pachirisu afterwards after the overgrown mushroom yielded questionable results. This means that he didn't use Pachirisu because he had a soft spot for the thing and slapped Follow Me on it just because it's what it did better than anything else, it's because Pachirisu gave him a chance to win more matches. Yes, maybe he genuinely likes Pachirisu. But since it wasn't his first choice, it's obvious that it's not the reason why he used it. No matter how much you want to believe the opposite, he used Pachirisu the same way he would a chess piece. He applied the same logic to this whole thing as any of the Smogonites you despise oh so much. It just so happens that he picked a Pokémon that rarely sees use by most normal players in most normal environments because of the restrictions of the 2014 VGC format. So please keep your annoying "YOU CAN WIN WITH YOUR FAVORITES" bullshit at the door.
Oh, I just mentioned chess pieces. That's something else. When have you ever heard the everyday Joe complain about how Russian grandmasters are obsessed with queens? Never. That's because chess players are above that shit. Not Pokémon players, by the looks of things. You never see some scrub brag, "I always underpromote because queens are so overrated!" Yes, underpromotion is something that happens, although rarely, most often to avoid a stalemate caused by a promotion to a queen. And that's exactly what happened this weekend. Se Jun Park used a seemingly lesser option compared to Amoonguss because the latter ended up dying more often because of its relative plethora of weaknesses than because he played it badly.
