Hiya.
My neddie dwarf was overweight when we got her. She lost weight simply by cutting down the amount of pellets, not by changing them. This did the trick and we have no sticky bottoms at all, especially since she lost the weight and can get to her bottom.
All of our rabbits only get an egg cup full of pellets daily, so maybe it's just worth giving less to start and not changing over at all?
You said your vet nurse mentioned seeing more bunnies with bottom problems since Science changed. I have it on a very reliable authority that it hasn't changed at all, only the packaging has. It mentions fenugreek but this has always been in the food. The new packaging was to attract the bunny parent.
Is my authority wrong? Do you know different?