That pulling levers in the basement furnace room wouldn’t blow the house up. It wasn’t until my 20s when it randomly popped into my head and I thought about it with my adult brain and was like “wait… Why would someone install something that would blow the house up?”
Not as such. But it also doesn’t mean that it can’t have catastrophic results.
Your water heater has an overpressure valve, but just one. A failure in that valve and a temperature regulator and you can have your hot water heater shooting up through your roof.
Your furnace has a control board. It turns the gas on, hits the igniter, watches for flame. An older, shittier designs, it was entirely possible for just one or two sensors to go bad and run the furnace to the point of melting down and have the house burned down. Source: happened to me on vacation many decades ago.
