Small carbs tuned for small engines can and do work well on 2X4 applications. The 390's being discussed are such carbs. When you double them up on a tunnel ram you're also doubling the fuel area. That's why they work. Holley recommends them for that particular usage because of the fuel curve.
When any carb builder specs a part number for a 2X4 application the air bleeds, emulsion circuits and supplied jets are downsized considerably.
The whole reason behind using multiple strombergs in the old days wasn't for the extra airflow, it was for the fuel curve. One or two of them wasn't enough for a 327, it ran too lean no matter what. Four or six of them was just right, together they would allow anough fuel to pass to keep it from running lean.
Take a pro stock engine in a fine state of tune and remove the tunnel ram, use one of the carbs by itself, with no changes, on a 1X4 intake and it will be too lean to work because you just cut the fuel in half.
The 390's in question will work on a tunnel ram because one of them would be too lean to use by itself.
I disagree with you on Musky2's icy manifold. Fuel may cool to a degree but only fuel changing from liquid to a gaseous state could form ice on an intake. If anything the carbs were slightly lean and only fuel that was atomizing well enough to cause a temp drop of that magnitude.
Not try to insult or bust anyones chops here. Please don't get mad.