I don't know if anybody bothered to tell them, but, in most people's minds, to suggest turning a positive ("WOW") upside down is to imply negating it.
IMHO, the better application of the reversal of text would be to say something akin to,
"Have MOM flip on Mother's Day." The "WOW" works just as well underneath as it does above, and the message is even more positive.
But maybe it's just me...