This regular haki is not a forcefield, that should have never been applied. Haki is armor, yes, but saying it's a forcefield is just completely blocking how it works.
It's an enhancer. When people make black blades, are they putting permanent forcefields around weapons? Did Vergo hit Smoker and Law with a forcefield around his Bamboo stick? No.
Rayleigh did not say "it is an invisible suit of armor", he said 'it is
like an invisible suit of armor", which is a
simile, which is
figurative speech, which is
not taken to be literal. It's stated to be that because it
enhances dura and AP, it does
not put a barrier around it unless it's advanced.
When they push Haki into people's bodies are they pushing a forcefield through their body? Are they putting forcefields through the metal collars? No.
Haki is everything but a force field, and with that, Haki resists certain things. Haki should not get power null because that's not how it works, it shouldn't getting forcefield creation in any state outside of it's advanced form.
These are my views on the "invisible armor". It's for the advanced.