The HVAC guys do not know anything about networking (why would they). The manufacture is looking at the total market, which is flooded with consumers that don't understand networking and problems everywhere. So they insist that a separate network be installed for their stuff (protecting themselves no matter how stupid the idea is). The HVAC guys only understand what the manufacture tells them, they don't know why or know any better.
But you have to be able to install a solid network every time, to debunk that.

My other paragraphs were going to be about the Araknis and why you are having problems. But it is rehashing things I (and several others) have talked about until we're blue in the face. I'm done trying to educate on that, use whatever junk you want.