No confusion required
Downwind abeam,
Using FAA International rules, you need to carry a reserve fuel amount equal to 10% of the enroute burn.
If you do the math you will see that is a large reserve. So all trans-atlantic (probably all oceans) operators dispatch to a city short of the destination with its' 10% reserve. Then a couple of hours prior to the short destination, you re-release to the commercial destinaiton with a reserve that is 10% of the new shorter burn.
That is the concept in big strokes. An international dispatcher or thourough review of re-release procedures can be even more precise.
It is perfectly legal and safe. In my opiniion, it is a way to update the rules initially promlugated for prop driven a/c in the old environment to make sense in today's envornment.
R