It seems like you are trying to start something, because any HVAC person I have ever worked with or known would laugh at the statement that colder air burns better. And the statement that there is a greater heat loss up the vent as conditioned inner combustion air is being removed from the structure.
My question still stands what kind of meeting were you at? As this might explain their thinking.

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Well thats my 2 cents.
Brian Kelly
Kelly Home Inspections