For CAP 371 airlines, the 45 minute report time is a fiddle designed to get the aircraft away as early as possible but having the crew report at or after 0600 local, before which the FDP would be restricted to 9 hours on a four sector day. From 0600, 10hr.45min are allowable.
All knds of pressure may be applied to get you to report early to get the show on the road (usually short of anything in writing, which the CAA might find interesting, so not much chance, Phileas)... you know the sort of thing, appealing to one's 'professionalism', 'conscientiousness', 'can do attitude' etc.
It's all cr@p. Conscientious, professional pilots stick to the FTL rules, which were designed to aid our rest and fatigue management. Anything else is unsafe and ilegal.
I aim to arrive in the crew room at STD-45min. If I'm a few minutes early, I get on with the job.
If the weather's cr@p, the computer u/s, the printer out of paper, the queue at security long, the aircraft parked a mile's hike away, I care not.
Strepsils
Standby notwithstanding, your duty time and your FDP start at report at home base in the case you are illustrating. The FDP finishes on blocks at last sector's end. Duty time finishes usually 30 min later, depending on your company's agreement with CAA.