Well it's called the bum-line for the pilot to 'sit' himself on and the teaching was to run that under the handle on the outside of the pilots door - clearly there has to be some margin for error so if the wheels are on that line there is still adequate clearance for the tips at the front.
It is also slightly more comfortable to err forwards than back, since you don't have a crewman in the door giving 'con', to be sure the tail doesn't end up too far back.
At 7:20 not only is there a crewman in the open door giving a con to the driver, but also waving to the adoring audience
There shouldn't (IMO) be any erring off the pilot's sight line on a small deck: it would seem that after rolling forward the main gear finishes up on the sight line which puts the SK some 6-8ft forward of optimum and by default, the tip path that much closer to the ships superstructure. On many RFA decks we had about 12-15ft tip clearance to the hangar so we would land on the line: not fwd, and not aft, and all without the crew leaving their seats in the back.
Small ship decks have a lot more to their operation than seems to have filtered down over the years; 'Corporate Knowledge' is the buzzword for passing on experience.