>Where people work, who have to empty a fridge before it can be remotely defrosted.

You don't empty a fridge with built-in defrost. Your home fridge defrosts itself every 12-24 hours and you don't have to do anything.

Normally, the temperature recovers in ~1 hour after a defrost. The attack is apparently chaining manual defrost commands one after another so that the interior gets way too hot.