FIRS 4/5 Steeltown: no vehicles/food required for cities in deserts to grow

In the past, when playing Steeltown on a tropical map, desert cities used to require food and vehicles (instead of food and water) to grow.

Somewhere along the line this is no longer the case and the towns don't list this as a requirement. I've tried it in version 12.x and 13, and FIRS 4 and 5 (alpha).

It used to provide a reason for sending food/vehicles to towns.