The grinding happened AFTER the U-Joint was out. They wail on the damn thing with a BF hammer and bend the lips of the bore all to hell then have to remove that material in order to get the new U-Joint back in.
You would be shocked to see what some folks use/do to remove U-Joints. It's probably the #1 job where people fail to use the right tool(s) (except maybe tie rod ends).
It would be one thing IF you were way out in BFE and HAD to change U-Joints on the trail with a minimal tools. But there is NO excuse for doing that kind of job in a repair shop.