It can be seals that buckle before the lid. It can be a tiny hole with a soft rubber stopper. It can be one of many things that cost a couple of cents extra and a bit more engineering and testing effort.
The cheapest disposable coffee cups I've used have a tiny hole for the express purpose of not pressurizing and spilling hot liquid everywhere.
There's a lot of conversation in the comments about "was there was an expectation that the pressure release valve would be there" There absolutely is a safety expectation that a sealed container of hot food is designed with a pressure release system.
BTW the fermented food thing is a misdirection. The pressure release system should have released pressure way before it even reached ballistic territory.