Because demand isn't even throughout the model year - so the lead time goes out when demand is high - that would apply to the caravan industry and certainly applies to the car industry.I don't see any reason why a caravan manufacturer can't, in principle if the necessary processes are in place, build any caravan to order with whatever options the customer has specified in much more than 4 weeks from scheduling to shipment, just like any car manufacturer.
The car industry imposes restrictions on options to maintain it's economy of scale - try getting any interior colour except black on many cars, even with a factory order.
