Indeed, there is no gain whatsoever in adopting a keyboard that puts all the most used characters in the home row if you're just tapping with two thumbs.
A better layout for smartphones, if one had to design it, would try to put all characters in two circles around the thumbs, while putting symbols and the least frequent ones towards the centre, requiring some extension of the thumbs to reach.
A better layout for smartphones, if one had to design it, would try to put all characters in two circles around the thumbs, while putting symbols and the least frequent ones towards the centre, requiring some extension of the thumbs to reach.