KMS I don't think there is much to disagree with regarding conservation of angular momentum - it is very well documented in the world of physics and it is why a skater speeds up when they move their arms inwards and vice versa - it is also the cause of precession in a gyro.
I would love to hear Mike Smith's alternative explanation for Nr rise in the flare, perhaps you can get him to post it here.
I'm sure it is very small distance that we are talking about the C of G moving but when something has a great deal of momentum ie a heavy blade travelling at high speed then small movements can create large speed changes. Try asking a skater to spin holding 20kg dumbells outstretched and the see how far they have to move their arms in to achieve their normal high rotational speed - a lot less than without the dumbells.
Vorticey - all the changes are a result of changing the inflow angle and thus the AoA of the blade - the AoA change moves the driving section and the flapping resulting from the AoA change moves the C of G.