^None of my other recorders, cameras, camcorders, etc. appear to be picky about cards, either.
I think most of us view Sandisk as a reliable, good quality card, and yet even within the Sandisk brand, there are a limited number of Sandisk models that are on the 70d list of approved media. And 70d users have to be very observant in choosing the correct approved model from among all the similar looking Sandisk cards at retailers.
The only other manufacturer on the list is Panasonic and the Panasonic cards appear from my research to be discontinued or very limited in stock.
If Tascam had published the list of approved media when they started selling the 70d, it would be one thing, but issuing the list months after the 70d has been on the market doesn't sit well with me. Tell me up front if a recorder requires specific cards to work correctly.