GPU crackers run in parallel;
Even massively parallel brute-force searches have to run through the search space in a certain order. Not all at once.
I'm counting on the guess that 'aaaaaaaa' will be checked really early, long before ';;;;;;;;', which I'd expect to be later, at least for combinations of that length. That is unless the algorithm checks repetitive combinations before pseudorandom ones, which would be a good idea.