I haven't run into a TO yet (me being one of them) that will uphold this rule.
Honestly this silly argument comes up every time, as is there's some loophole you can exploit to get around the rules. But that loophole simply doesn't exist, because everything is at the discretion of the TO.
And here is where we agree. This is a silly argument, and you're right that the only safe bet is to have the correct cardboard.
That being said, wither you find my wager silly or not, I'm counting on FFG to do what they have done in the past; do away with silly rules that do not effect the game in any way.