My friends often joke that a person who is checking our tickets is able to do precisely this mentally in their head – when that person is satisfied by seeing a QR code rather than scanning it.

It became very popular over here with the Green Passes (EU Digital Covid Vaccination Certificates). Waiters, etc. were supposed to check whether the guests are vaccinated, but 99% of them just demanded any random QR code to be shown to them, took a look at it and considered it done.

Unless we are a country of hidden math geniuses :)