Well, yes, theft on low Control. But I've never heard it called spoilage.
I call it spoilage, because it's consistent and a theft-free alternative exists. Using ox carts when one could use caravans is nothing else than throwing that food away. The quantities are small if control is high, but I've seen over 95% of the food in a transfer getting robbed. And even with good control, you'll lose some.
It's spoilage by handing it out to thieves, even if it doesn't rot, because that lost food is worth more than the cost of the caravan needed to send it.
And I wouldn't consider 5% to be negligible. In D'Hara, a 5% drop in food stocks is often the difference between making it through a year without starvation and having Port Nebel revolt to five different realms in the same season.
