I've never heard of checking the mixture control during a runup...got my first instructor ticket over 30 years ago.
I do think people overlook proper use of mixture during takeoff at HIGH altitude airports though.
People should also check the prop if equipped with constant speed prop.
speaking of glides/engine out practice....using the RPM knob to ''pseudo feather" the prop during glides, does extend glide range...indeed some glide performance charts require prop to be adjusted.