Now, while I think he's likely guilty, I actually could see a way those specific cards got marked as I've had a somewhat similar situation happen before. It was just an FNM, but I only had a 40pack of new sleeves with me to re-sleeve my 60 card deck. The sleeves weren't 'bad', but I prefer them new and clean, so I put those new ones on. Only later did I realize I had basically sleeved all the non-lands as I had the deck sorted when I did it, and there was like 21 lands. So, 39 spells and 1 land got new sleeves, and the others were ever so slightly worn. If this had been a big tournament, I would've just bought another pack and re-sleeved the whole thing, but I didn't even notice till the tournament was over. Once I saw it, it was possible to tell if the top card was likely a spell or land.
So, for Yuuya, maybe he had the deck sorted out and was showing someone it. Those specific cards could have been all in his hand when he banged the corner on the table to crease the corners, or just how he held them creased the corners. It's less likely than intentional cheating, but I can at least envision a way it could have happened accidentally.