And everyone knowing that trim issues are complete rubbish as 'they' only weigh 80Kgs, not 800kg, know exactly what the weight and distribution of the cargo in the cargo holds and the trim of the fuel tanks are of course.
Weight and balance sheets are produced for the seats the passengers are booked into. My personal approach is that I require passengers to occupy assigned seats for take off and landing UNLESS I consider there to be enough flexibility in the trim to permit movement.
I would assume the Captain on your 'one man' flight would be the same. Light loads with cargo and fuel can produce trims very close to the limits. Many carriers stock the holds up with cargo when the passenger load is light. Just because there is no-one in the cabin doesn't necessarily mean the flight is 'empty'.