Is the forum really telling me that I could not flip a rear wheel if I was doing a ride with some serious hills towards the end - and I needed a lower gear to make my ride pleasurable?
According to the rules there's nothing to say you can't.
According to the spirit you shouldn't. You should either suffer with a low gear for the flat part of the ride in order to make the hills at the end easier, or ride the first part with a big gear and suffer in the hills at the end, or find a pyrrhic compromise.
I did the whole of LEL on 67" without a problem, even with that tailwind across the flatlands heading North on day 1. If I need multiple gears on a ride I'll ride a bike with gears.
On the LEL recce ride I did in March '09 I did swap gears between days 1 and 2, but I'd entered the rides as individual DIYs (300,200,200) so there was no change of gear during a ride. What it taught me was that it's more hassle than it's worth and to just HTFU and pick a gear in the middle and get on with it.
Do what you want, but don't be surprised if you get the odd sharp look from people who would prefer the FWC to have an explicit rule preventing gear changes mid ride.