[Legbreaker]

Even so, it's just plain bad practise to hand over payment prior to receiving the goods.
As an example, if you were buying a new luxury car, would you really hand over every last dollar weeks before even laying eyes on it? No, you'd probably only go as far as laying down a deposit and hand over the rest of the cash when you got the keys.
The same logic applies to the oil and the German shipping (page three again - NO mention of US ships involved besides the USS John Hancock). The Germans aren't stupid. They're sure to retain absolute control of the resources involved until they've got what they're paying for.

One other point is that until the last week or so, nobody is likely to know just how many people will be boarding the ships, and it's also likely that involvement of a few ships remains uncertain (ongoing repairs, etc). With that uncertainty, the Americans could manage to slip in half a dozen tanks, a truckload of electronics, ten tonnes of valuable medical supplies and so forth - the Germans would be doing everything in their power to prevent that.

My belief as previously indicated is the Germans would only part with a minimal amount of oil necessary for getting the ships to the point of ready for departure. An inspection would then be carried out by Germans and the ship would be allowed to move to the fuel point to fill it's tanks. This may well mean the passengers are cooped up aboard ship another couple of days, but at least they've got a roof over their heads, food supplied, nobody shooting at them, and they're on the way home.