As with most recalls, they do not affect all of the vehicles. Many on the various forums, which in total probably equal a very small percentage of owners, never had any problem with the Workhorse brakes. I never had any problems but I used my coach a lot and also flushed the brake fluid often.
If you find a W20, W22, or W24 that you like, don't worry about some recall that was taken care of years ago. Buy it and enjoy it.
If you search brake problems, you will find out that occasionally people have brake trouble on Fords, and even DP's.