Not necessarily. I have used cheap food thermometers that took upwards of 60 seconds to settle on a temperature. If you weren’t aware of this flaw you could easily read the temperature after 10-15 seconds when it seems to be settling down and end up way off from the real temperature.

I always have this conundrum when cooking a steak on a hot pan: Is the thermometer still settling down or is the internal temperature actually just rising quickly?

That's exactly why I got a Thermapen. I don't need to ask that question anymore.

more likely out of calibration