How long until you start questioning if it will work and invite doubt? Or will you assume defeat if the vampire fills the gap with, “why, thank you my good sir”?

My understanding of the idea with many interpretations of magic is they are all just ways of focusing your will on the world.

Ergo, the words aren’t themselves the source of power, your expectation that the words will result in a certain outcome is.

Therefore, if your intention is to deny entry is strong, there could be a fairly good gap.

But on the other hand, playing around to try and see could create doubt and uncertainty, weakening the effect.

The good ol’ Red Scare.

It’s not that there is superior heat output, it’s that there is superior heat collection and observation.

Not familiar with the meme directly, taking your attached picture example I can guess why they think it’s better:

It’s trapped closer to them.

Heat, that you recognize exists but usually rises out of reach of an uncapped candle, to the ceiling, is now trapped near the observation area. The pot is trapping it and radiating it much closer to the person thinking they’ve just solved the universe.

It’s observable. Like people who don’t understand the need for vaccines because they’ve never personally seen the disease the vaccine helped beat down, a majority of people struggle to grasp theory, and direct observation is all they understand.