Steer Jock- my layman's terms- used car sales man. They look, find and sometimes rehab projects. Then they market their finds. There are some steer jocks that breed and sell but most seem to buy low and sell high with the additional services on occasion of fitting the animal after the sale and advising on feed etc.
Professional Fitter- An individual who fits cattle for their profession. I also know lots of folks that fit cattle that do not jockey steers.
OH Breeder.. I totally agree with your definitions. In my lamely worded statement that they were one in the same, I was referring to whether they should be allowed to clip at the jr shows. If you're trying to keep it down to just jrs and their families, I can't see a difference in a steer jock or a professional fitter doing the clipping, neither is family. (unless you're lucky)