All holsters will cause wear...This is the nature of the beast...Kydex is a bit better in this regard because you can "fit" the weapon at the trigger guard only...this causes minimal wear...
With a leather holster that isnt "lined" we still have to fit it a 2 places...Trigger guard and ejection port..this can cause a bit of wear on the edges of the frame, but not to any great extent...If made correctly, the weapon with have a slick little click when placed back into the holster...
"ONE SIZE FITS ALL" holsters are notorious for causing wear spots...They arent molded to fit and shift because of it...
BTW...most holster makers dont use "liners" anymore because of the quality of the hides that we can get these days...Most times it is done just for the "look" of a lined holster, or at customer request..
just my .02 cents