Pretty much all flash cards do this to some extent. Actual flash chips themselves are dog slow individually (well, below 10MB/sec to a single die, plus there's your flash translation layer overhead given that you can't erase single "sectors", hence there's a lot of logical remapping going on).

I think the faster ones have multiple buses and can have multiple concurrent operations per bus, plus enough buffer memory on the controller to be able to do things fairly optimally. It can get pretty hairy making NANDs go fast in my experience

Hugo