They didn't actually hit 50C, right? I read it as setting the thermostat to 50C, which basically would just turn off the cooling compressor entirely - not heat the fridge.
So far as I can tell, the thermostat was set to 150 C, and it actually reached 50 C.
Though given how easy it is to make the error, "150" may have been a fat-finger typo for "50".
I read somewhere else that they activated a quick defrost function and as those were industrial fridge, it seems they can heat to 50C