And that's the overwhelming majority of cases. Wanting to select an item starting with the same letter repeated twice is rare. It makes sense to speed up common cases at the expense of rare cases.
Not really since those rare cases are more memorable, so in addition to other UI elements having different behavior (though I admit this is the much bigger factor) you don't treat this as a reliable mechanism for search. So you'll just enter the next letter as you do everywhere else, and your frequency balance changes
And it especially doesn't make sense for such an long-standing core UI toolkit to not have these kinks ironed out. These behaviours are already handicapped by their obscurity, no reason to make them behave counterintuitively on top of that
As a long-time Windows user, I simply have to disagree. I use both methods constantly, and removing one would be a significant degradation in usability. Whenever I have to use software that doesn’t have them I miss them sorely. The rare case, on the other hand, is so rare that I don’t even remember the last time I came across it. It is negligible.
The behaviors also aren’t that obscure, assuming you learn that you can select by typing a character in the first place. When used regularly, you then rather quickly learn what happens when you type multiple characters.
