OK, sure, it's a possibility, but your/the other guy's claim was that clear sleeves aren't tournament legal.
This doesn't seem to be the case since, at least in the 2017 Play! rules I found, I couldn't find a single mention of clear sleeves. More than this, the official rules make it clear that sleeves are optional: "IF a player's cards are sleeved," "card sleeves CAN be used," or, significantly, "players should keep in mind that card sleeves are not a requirement at Play! Pokemon tournaments or events."
Bonus meme: "Cards printed with any other back may not be used in a Play! Pokemon tournament, even if sleeved with opaque card sleeves" (why mention opaque sleeves if only opaque sleeves are legal?)