I would say they used the wrong post. When you buy those posts they have a weight rating for how much they can support. You can't just stick a post in and hope it will hold up your house.
You need to determine what is required BEFORE you remove the wall.
As for fire, roof trusses are one of the worst things yet they are used all the time. What happens in a fire is all the metal connecting plates heat up burn off and then the whole truss falls apart into sticks.