This happens around the world dont get worried to much. Its just that general tires is the only company making tires locally. So assemblers have to keep a extra supplier just in case.
Mercedes, Audi, BMW all over the world companies do this. You can see some BMW with continental tires some with Bridgestone tires.
SWIFT DX and DLX had same size but DX got Yokohama and DLX got Bridgestone. Now DLX comes with Yokohamas
PS Swift and Yaris have the same tire size.