I messaged Dan Schwank (Red Rose Reproductions - https://redrosereproductions.com/) who is manufacturing and selling Miter Jack Vises (Donkey's Ear) and his response to my question: "why the plane doesn't destroy the face of the clamp?"
Dan: "Oh it can if you are not careful"
"I tend to use it with a plane and stop planing just before the workpiece is flush and a very fine set on the plane"
"For small work I pare with a chisel. A lot safer in practice."
Hank: Ah! So it is all technique, not a feature in the vise."
Dan: "Yes, I would say it is technique"
Dan: "I should add that the working surfaces can be dressed, and probably will need to be occasionally as nicks and cuts can and do occur"