It's not sharp pencilling. It's logging time as 'Pilot in command' of an aircraft. You could log 'flight time' separately I suppose.
The big companies who need their pilots to 'fly' 800 hrs a year need that extra 10 minutes knocked off each start up. Can you imagine how many hours it saves say CHC/Bristow/Bond in ABZ per year in pilot hours? Bloody loads I bet. we can start up and easily sit for 10+ minutes before taxiing.