Why on earth would you think that? To my knowledge, not one of the five transports available to Marines uses 'wears Terminator Armor' as a way of differentiating between unit types. Rhinos and Razorbacks specifically exclude Terminators, and the others all list a specific allowance for certain numbers of Terminators. If anything, you've got to show that your basic Space Marines are wearing power armor if you want to cart them around in a LR or LRC, though the other three don't require the Space Marines riding in them to be wearing power armor.
I also have to wonder why you'd ever have a need to transport more than 5 Terminators.
Just had a quick glance over the Chosen entry in the Chaos codex, and I'm not seeing where it says that you can give any of them Terminator Armor. Granted, it's very much implied that a Terminator is wearing TA, just like in the SM dex, but I'd certainly argue the point if someone tried to claim +1A benefits.