I've seen some (first models and maybe all/most of them made for the first couple years) that had the longer threaded barrel and the taller suppressor usable sights on them.
Then the urban gray model came out and it had the longer threaded barrel and taller suppressor sights.
Then, a few months ago, I started seeing the "what???" version at the gun shows. It has the longer threaded barrel - but standard height sights. Not sure what it's for unless they figure some people will replace the taller factory sights with aftermarket sights anyway??? I don't know. I just know it looks funny with the short sights on it.