Believe it or not it is completely impossible for your throttle to "freeze up" as you are contending, it's basic physics. You are perpetuating a myth.
It blows my mind as to what extent people can argue for a lack of necessity of a repair or replacement of a 30-dollar part.
But since you invoked physics, I'll bite and waste some time here. Just so we keep a Discoweb tradition of keeping misinformation at bay.
You are driving along, on a sunny 80F day (about 300K), at sea level, at about a third of a throttle. Your manifold pressure is about 7.4 psi (about one-half of atmospheric pressure).
What do you think happens to air that goes from atmospheric pressure to one-half of atmospheric pressure behind the throttle plate, in a matter of milliseconds?
[You as] a person enlightened in basic physics will know that it is pretty close to adiabatic expansion. When a quantity of gas experiences a drop of pressure, it experienced adiabatic cooling.
Wikipedia has all relevant basic thermodynamics info on this subject; I will skip all derivations and just tell you that the 300K/80F air drops down to ~246K, or ~-17F.
There's not a slightest doubt that the moisture contained in the air will freeze. The question is how does it apply to the throttle plate, throttle body, and things around.
There are several factors offsetting a pretty gargantuan temperature drop -
(a) laminar boundary layer - the temperature drop actually occurs away from the throttle plate itself, because the air velocity on its surface is zero. So it gets cooled off, just not directly but by convection and by radiation (of the plate, not of the air).
(b) dilution of the cool air by the volume of air inside plenum / intake manifold (which itself sits on top of the engine and is usually warm).
(c) heating of the throttle body from everything else outside it in the engine compartment.
So the question becomes if/in what conditions air cooling is of sufficient concern. Again, for FAA it seems to be a pretty cut and dry case - the aircraft engine, regardless of whether it is fuel-injected or carburetted, WILL sooner or later experience these conditions and therefore MUST have remedial means. I quoted you the regs, but you, as a pilot, should have known this (but since you, as a self-professed basic physics-educated person, should have known that there is zero difference in principle of adiabatic cooling between a venturi and throttle opening and don't, I don't have too much hope).
For ground vehicles' engines every manufacturer weighs the engine layout (e.g., how good is heat transfer from the engine block to intake and to throttle body), the cost of throttle body heater implementation, and the liabilty from both sides: customers who'd bitch about every coolant leak vs. customers killed in accidents when they find themselves with open throttle. Some manufacturers save money by optionally installing it on vehicles in excessively humid or cold climates.
Land Rover decided to do what they thought was right for Land Rover and installed thottle body heaters. Of course this particular D2 part happened to be one of many fuck-ups BMW brought in its brief ownership of Land Rover; it is a lot less frequent issue in pre-Bosch vehicles (as far as I know).
Now, as far as battle cries for evidence: there will be next to none "anecdotal" evidence of this ever happening, because, should it happen to you, you'll think "WTF???" and try to kill the engine/downshift/brake/slow down and pull over. By the time you pop the hood and start fiddling with throttle cables, it will have melted and everything will be peachy. I believe the only real evidence and statistics can come from manufacturers who have the most experience with drive-by-wire throttle controls, like GM - but I don't think they'll be very open about it.
To conclude: the chance of throttle freezing over is about the same as the chance of a brake line snap, with the same consequences. The decision on whether to replace a $30 part or argue about a lack of need for it is all yours.
By the way, Jimmy as usual gets the grand prize for mention of RightStuff instead of paper gaskets with this part.
