You live where it can get very cold, the advantage of bypassing the heater is that they are notorious for leaking, even when just replaced. If someone never drives in - 20 or lower Temps, the TBH won't do anything but be a leak source.
If they didn't leak so very often, it wouldn't be an issue, but it's near a 100% leak rate.

 

Still not worth the risk to me, even though I’m in a much warmer climate.

 

I could certainly see the C/C cable freezing up. They mounted the darn thing right by the shock tower and it could easily collect ice over time and if engaged not disengage. I wasn't there so it's just a guess, but like I said about 90% of well know 4x4's out there do not have any kind of throttle body heater and absolutely zero reports of it happening on the Jeep, or Hummer forums which I used to be on (and only the 4.0L I6 Jeep engine had the TB above the exhaust manifold all the rest had the TB in front of the motor where it would be much colder vs the Jeep/LR setup). If you don't live in Canada or Alaska and in -30F weather you are running a very strong risk of letting your THOR setup slowly kill itself. It's a pretty sneaky killer, and once you reach that critical low coolant level it's a matter of a few minutes before that engine overheats and causes $$$$ damage over a 30.00 part.

I have bought 3 D2's with blown motors out of the 3 2 of them for sure died from the TBH leaking. The previous owners did the usual hose replacements, new water pump, and even a new radiator, but one look under the throttle body and it looked like something from Alien with white/pink/red goo all over the TBH plate, the valve cover, and even down along the block. They dumped all that $$$ into fixing the cooling system but failed to fix the weak link in the system which was a slow killer.

You guys can do whatever you want it's your LR, I can only give you my advice from the many many many years of working strictly on nothing but LR's from 87-04. I have traveled in very cold conditions, and I always ended up doing like what most 18wheelers do in severe cold weather and block off most of the radiator surface. That allows the engine to run warmer, better heater output, and it'll get your engine running warmer as well which would mean the temp under the hood would also increase.

 

I’m sure it was the cruise control cable and it’s coincidence that it only happened in the brief amount of time the TBH was bypassed. Traveling through cold weather and living in it are two different things…

I’m not trying to convince you that I’m right, I always throw it out there for those who are in truly cold climate to consider. If it hadn’t happened to me I would have thought you had a good point and not given it a second thought until it was too late. To me and where I lived it would never be worth the risk to bypass it.

I’ve had 3 D2’s and never had a leak at the plate. The problem I had I caused because I broke the nipple on the reservoir while moving the line attached. Those Disco’s you described didn’t die from the TBH, they died from poor diagnostic skills.