How to remove bathtub faucet
I called Kohler support.  They told me "it just pulls off".  I was disappointed with that--nothing after 5 years "just pulls off".

I ended up tapping the hole. It's just the right size for a 1/4-20 tap.  I then used a bolt to pull the inserts off--just screw the bolt in until it hits the valve stem and it pulls it off.  I'm enclosing a picture of the inside of that insert so others can see what this is.