This is such atrocious modeling.
So, I have witnessed ammo cook off in the turret ammunition compartment from an engine fire…however it took about 45 minutes to happen.
As long as the ammunition compartment has not been compromised, it would take a while for heat to reach sufficient temp to cook off. It’s probably a “balancing” mechanic.
Probably same treatment as crew repairing tanks in less than a minute while IRL some parts could take half of hour to next hours IRL.