Not necessarily. Eg.: A decomposition: out of one molecule you get two of then, no energy transfer but increase of entropy.
"Heat" is not the property of a system. We say a milkglass is hot. It's wrong; It is not hot until you put your cold fingers on it.
This, and the whole part about PLank's law is on spot! It shows exactly why it is inexact to associate heat with IR.
Also, you feed energy to a molecule, it is the property of that molecule how it will give that energy back:
The best example is:
You give energy to a light bulb, and it gives light.
You give the same energy to the Track IR emitter on top of your screen, and it gives you IR.
Question: which one is hotter?
As a bottomline, a IR receiver has *nothing* (in this context) to do with heat. Yes, IR emitters are to some degree "hot" if you touch them. But saying they emit IR because they're "hot" is wrong. It is just the explanation given so that normal Joe can understand it.