I agree with you there 100%. Except it distracts from the concept. The concept is time is up. There are no more minutes left. A thermometer rises and lowers on the whims of its climate. A clock measures our lives to the seconds. Hence its metaphor.

The metaphor began because it thought it would causes a greater detonation. It didn't, they made it bigger. Then they armed the planet. Until it has evolve outside of weapons.

The clock can wind unwind and stop. It chimes its tolls. It always was significant of its historic cycles. Mayan, Egyptian, Summerian etc. A thermometer is a bit more fickle.

However you perceive its event, it is only theory.