I still don't get it.
Our big tent (Equinox 450 IIRC) is a tunnel design, with vis-à-vis bedrooms. We take down the small bedroom as a matter of course when packing, purely for ease of stowing. Last weekend, with dry conditions for a pack, but boggy ground from three days of on and off rain, we dropped the large bedroom, and put in the sun for the groundsheet to dry. If it had been raining, we would have packed that straight away. Then the fly comes down last. I have done a complete pack inside a tent, before emerging, putting the panniers on the bike, dropping the fly, and going. If I had had an inner-first tent, it would have been exposed to whatever rain there was both in erection and strike, and, getting a wet fly off a pitched inner without brushing, spilling or otherwise wetting the inner is quite a skill.