Hahaha, cost cutting PTC style!!
thing is, youre actually right. PTC get charged every time the fuel truck is called over, so it saves them a few bob not to refuel after every flight.
however, seeing as there is only 5.5 hours endurance in the seminole, and each slot is 2 hours flying, it would seem prudent to refuel after the second flight!
another thing, from past experience i know that with 2 people in the front seats and no ballast or pax, those seminoles are fairly close to the forward cg limit with full fuel, and the arm moves further forward the more fuel you burn, so im guessing the iaa may have something to say about their weight and balance sheet, as well as the whole lack of any fuel reserves, or any fuel at all for that matter!