I own this one, barrel measures 3-1/4". Whoever did the modification did a great job on the front sight. Yes the pin does stick out a bit further than normal but does not hinder operation or in my view create a problem. Not being a S&W mechanic I cannot explain the reason other than the possibility a different model pin may have been used.
This one was also a Brazilian Model of 1917 I picked up from a friend, it had been nicely refinished which made it a candidate for further modification, I had a friend of mine cut it down to 4" and mill a Baughman style front sight regulated for the Wondersight rear.