Who says they were actually transferring fuel and not just using an opportunity to practice hooking up ?
Hooking up or not, fuel flowing or not, certainly as I recall it back in the olden days most towlines ( but not all, as Beags mentioned there was one over the southwest UK) ) were over water, working on the principal that if at all possible you wanted to avoid the chances that if things went wrong the, err, , bits, didn't fall on the general population...I'm not talking big airplane size big bits....I'm talking about spokes, or on occasions whole baskets and bits of hose..in fact thinking about it hasn't there been at least one case where the basket and hose departed company with no assistance from a receiver...
Not that I ever had it happen to me of course ( I generally was a slowly slowly..slowly...missed! merchant) but I know one or two individuals that did manage to remove one or two components from drogue... .....