I had a 4" M13-2 that apparently didn't have a crosspin...until I had a dovetail cut so I could install a different front sight, then the machining did something to make it obvious.
Admittedly, a 13-2 isn't a 13-1, but that sure looks like an improperly installed S&W front sight. I'd try to find a loupe or something else that could provide magnification to determine for sure whether there's one there.