That's true for the standard tactical and field model 93os.
However, the 9-shot JM Pro, model 85119, does come with a 22" barrel that's threaded for the Accu-set chokes. I haven't seen an individual part number listed for the barrel anywhere, but you can call Mossberg sales at (800) 363-3555 and ask for a replacement barrel for a model 85119. It'll likely cost you in the neighborhood of $200-$250 and I seriously doubt you'd be able the get the barrel anywhere else. Keep us posted if you're able to get your hands on one...