ALL holsters will wear the gun's finish.
Kydex will quickly wear the areas where the holster makes contact with the gun, but the wear is self-limiting. It wears just so much, then pretty well stops.
In addition, a GOOD Kydex holster will wear ONLY the contact points.
Leather seems to wear the finish less, but what's actually going on is, the leather is stretching and forming to the gun, and actually wearing a larger area.
As the holster forms to fit, the entire finish is worn, not just some contact points, and the wear continues as long as you use the holster.
There are one or two Kydex makers who line their holsters with a synthetic "suede" to help limit wear.
Bottom line, ALL holsters will wear the finish.
Kydex will quickly wear the contact points then stop.
Leather will wear the entire finish off.