The copy of the log book I have of a chap who qualified as an Air Observer in 1941 Has entries for air navigation, bombing and air gunnery courses. A total of 18 hours flying was all that is recorded to the bombing and gunnery phases.
His log book records his trips with Bomber Command as Navigator until he becomes OC 10 Sqn when they are logged as Air Bomber. When he goes out to India after 10 converted to the Dakota he logs his trips as Co Pilot.