I agree with you 100%. Personally, double-walled tents don't make much sense to me: they are just extra weight. Most of what is referred to as "double-walled" tents in the marketplace are in fact mostly mosquito netting inside a single-walled tent. IME this does nothing (except keep bugs out). A true double-walled tent, for the topic in this thread, must be two SOLID walls, inside breathable, outside waterproof, set up to actually trap some dead air between. This is hard to do, for me. And, on a still night there is going to be condensation, no matter what.
Either way, frozen condensation inside one's sleeping bag is a very real problem. If it's 10F inside the tent and your body is 98.6F (assuming your not dead yet), then it is 32F somewhere between you and the air in the tent: that puts it inside the sleeping bag! There is no other outcome given the situation.
So, Frank, you are right! We would be better off preparing for that inevitable situation than worrying about condenation on the tent walls. I can see various solutions for this problem, given different circumstances.
Since my winter trips are confined to one night out (although I prepare for two), my solution is to carry a better down bag than what the temperature is expected to be. For overnighters, an extra few ounces of down is the most efficient solution that I have found.
However, a longer, multi-night trek in winter where expected temperature below freezing night and day is an entirely different matter. For that situation, heavier and bulkier synthetic insulation is probably necessary as well as perhaps, vapor barriers.