Lowering collective = nose down
It is kind of amusing in retro spect to see how speculative and complicated answers tend to be.
I would use the following example: what happens to a plane if you remove the forward wings....
You can of course start a whole thread on how the tip vortices of the forward wings react with the tail, but the fore most important thing is that you remove upward lift at the front of the air craft, so all other things equal, the nose must come down, that in fact is exactly the purpose of the tail.
Perhaps a more serious result of that: high speed low level flight in a heli is more dangerous than planes: if you lose your engine your nose may point faster to the ground than you are able to recover by putting cyclic backward while flaring...
m2c, d3