It's as if the person who wrote the algorithm thinks that the least likely thing someone would get wrong is the initial letter, and that it's pretty safe to assume that someone trying to write 'gravel' or 'travel' would of course know what the first letter was, so they don't consider the possibility of the first letter being wrong.Fair enough - but that may well be an illustration of another point I nearly made - that most spell-checkers seem to have difficulty if the initial character of a word is incorrect.
'travel' for one.Nevertheless, I agree that if it considered the possibility that any typed character might be an 'adjacent key error', it would presumably have suggested "gravel" (and maybe lots of other things!).
They also are completely flummoxed by punct;uation marks. To some extent you can understand that, but then when there are two misspellings either side of a punctuation mark, or either side of an erron eously struck space bar, where removing it fixes both of them, you do wonder why that isn't looked at. The processing power of modern PCs would be more than adequate to allow very complex checking to be done.
The more I think about this, the more I wonder if they are only allowing for genuine don't-know-how-to-spell errors, and not at all considering finger fumbling on a keyboard.