Are you sure that prose and single-character button labels have the same readability characteristics?
The same property that makes "BIG TEXT" more difficult to read than "small text" might make each individual character easier to read. I'm not sure that it does, I just don't think your wikipedia page discusses this at all.
The same property that makes "BIG TEXT" more difficult to read than "small text" might make each individual character easier to read. I'm not sure that it does, I just don't think your wikipedia page discusses this at all.