I would guess a short trip would be one where the car isn't able to get up to operating temperature so for a petrol car might be 10km and a diesel 20km?
In cold climates they have products to assist like block heaters and VW fit components designed for that region so it's possible that cold starts here during winter could be just as harmful as cold starts in a cold climate.
Comes down to the owner using some common sense, if they have a few cold starts a year and rarely go WOT and mainly drive long distances servicing at 15,000kms intervals is probably fine but if you do shorter trips and/or go WOT often it would be beneficial to change the oil more frequently.
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