The revolver's muzzle and sight peeking out of the holster's muzzle doesn't seem justifiable. S&W made that change to their revolvers -- shifted from 3-7/8" to 4-1/8" barrels -- in the 1970s, for fear of anything under 4" being outlawed as Saturday Night Specials (remember when that's what we worried about them vs. AK47s?).
Which then suggests that the holster was made using a VERY old mold, of the old Smiths. At Bianchi we learned the hard way when the M27K quite suddenly stopped fitting customer guns; S&W didn't tell ANYone, and in the 27 the muzzle by design rested on the inside of the holster, to prevent tipping the gun out from the rear by the grips.
In the case of this particular holster one would wonder about that front sight insert being pulled loose at some point. Something the maker, not the buyer, should've taken into account

.