Should a castrum be producing supply when it is under seige? I was beseiging a castrum for months and months and was wondering why I hadn't starved out the garrison. Turns out the castrum is generating 4 supply points each turn even when beseiged. The garrison troops will get pretty weak but I don't think I will ever starve them out because their strength will stabilize at whatever number of troops are supported by 4 supply points.
Is it intentional for castrums to produce supply even when beseiged?