This is true, But I'm in NSW, it doesn't get THAT cold. Plus I left the stock cooler so there is a bit of heat transferred there, Certainly enough to warm the oil enough to get it moving. Just flick the heater on to open the thermostat and get coolant flowing faster.
I'm not sure who would be running mineral oil in their car at this point though either.
I have seen someone make up some aluminium cover plates for their oil cooler for the colder months. Less moving parts, less that can go wrong.