What's supposed to happen when you opt out of face scan at US airport?

I went through DCA and specifically told the agent I did not want to do the face scan. He then asked to see my ID, next he put in a scanner, then gave it back to me and waved me through.

I thought if you opted out they would simply request your ID and visually verify you with no extra scanning. Is this normal?

agent airport back next opt out privacy scan scanner thought