The tip path plane is the real judge of what is going on.
At the front in forward flight, the tips and the TPP are at its lowest position - relative to ANYTHING - and it then climbs around the retreating side to reach its highest point over the tail boom. It has flapped UP to get there, and then it flaps DOWN to get back to the front. Relative to the horizon, relative to the aircraft, relative to your maiden aunt, still flaps down at the front and up at the back.
The advancing blade has to dump most of its lift to match the 25% of the retreating blade that is still producing lift.
As you say, the TPP doesn't necessarily match the swash plate - I think the BO105 has its swash plate working at 90 degrees to the direction of travel? All depends on where the pickoffs are.