It's pretty easy to not touch your face when your hands are physically on the handlebars. As long as you are able to wash your hands immediately after getting off the bike, I think you are reasonably safe.

It's not expected to be perfect and immediate. It's about lowering risk as much as feasible and defense in depth.

I don't think that's true. People can get a lot better at it in a relatively short period of time. I have.

Face touching is literally unconscious in many cases. It's entirely possible you've been touching your face and not noticing it, but have just become more conscious of the times you attempt to stop yourself from touching your face.

Moving your arms isn't like breathing. It's not some autonomic nervous function.

If you aren’t aware of this those ML apps that beep when you touch your face are pretty surprising.

Also there’s the whole psychological thing about telling someone not to do something when it was previously largely automatic, making people do it more. Like having an itch or imagining insect bites.