I have recently surveyed this area in person, and have noted a street sign reading "Hutchinson Street" on the NW corner of Hutchinson and Milton Avenue. As far as I can tell, this is the first sign that indicates Hutchinson Street going from NE to SW along the way. All other signs east of this location indicate West Hutchinson all the way to the busway. There are signs continuing SW that all indicate Hutchinson Street. On the corner of Braddock and Hutchinson, there is a sign on the NW corner that indicates West Hutchinson Avenue.
All of this to say that it seems that as far as the posted signs are concerned, the point at which Hutchinson Street becomes West Hutchinson Avenue is at or very near to the intersection with Milton Avenue. This is confusing to me because apparently the street-to-avenue transition occurs in the middle of Swissvale borough, away from the borders of either Pittsburgh  ( near Laclair) or Edgewood (Braddock). I would have expected the change to occur at one of the borders. I suspect that the sign that indicates West Hutchinson Avenue on the NW corner of Braddock & Hutchinson might be a mistake by Swissvale DPW, as I have noted that they have incorrectly changed a few other street names.