i asked a lot of asian people, my parents too, about this and they dont have any coherent, reasonable explanation for this theory.
I talked with my chinese medicine doctor. his explanation seems better:
basically, humans weren’t designed to intake vast amounts of cold fluid. it brings a shock to the internal tissues that operate at whatever 38.x degs. [remember when you have a brain freeze or a icy/smoothie freeze in your head that really hurts? kinda like that) maybe cool water is ok, but obviously ice is even less appropriate. overtime, this especially affects the neck muscles as well as the internal system/organs (trans?)
(i had problems with this, stopped drinking ice cold stuff and my neck has been better. coincidence? i dunno, but it’s working)
so some of you may wonder, what about freaking eskimos and arctic folk [maybe they do heat up their water, anyone know?], dont they have to drink cold stuff? to which his answer is:
They live in a cold environment and the body (from external stimuli) understands that it is in a cold environment over a long period of time. so the body has adapted over a lifetime.
This contrasts with most of us who either live in a temperate, tropical, sub-tropical, or urban setting where our bodies are subject to a warm environment and responds accordingly.
in short, he said drink/eat stuff that is consistent with your climate (at least for coldness. this doesn’t apply the hot side. and i hope you don’t go around drinking boiling liquid)