I wouldn't trust a phone rep or marketing intern to get the tech specs right. It wouldn't be the first time they screwed up (like the Lexar 633x 128GB MLC rumor started by a well-meaning but misinformed rep). If they managed that, they would be the first in the entire industry, and it would be major news they wouldn't keep to themselves.
There may be some MLC cards out there claiming U3 speeds, but U3 microSD cards in general (much less over 64GB) are no indicator of MLC NAND, and over 64GB are a near certainty not to be, without being accompanied by a press release trumpting their industry-first breakthrough.