Jipe---It is hard from riding the bike to tell what bob is from (Pedal or Rider). It is very easy when looking at the bikes from the side to tell. I have no doubt the Birdy has more rider induced bob.
With the Moulton front wheel stopped by a wall with you on your bike add power to the pedals. The BB will go down... Power induced bob---you cannot avoid it with the pivot located where it is.
Schwinn and other companies moved the pivot up from the bb (Sweet Spot) and that still did not solve it. Just the action of adding power to a URT causes Pedal induced bob.----It is probably very minimal with your Moulton---which is an awesome bike by the way.
Just the transfer of weight from the upper frame to the lower frame when applying power with the URT will create bob. Search "URT Bike Wikipedia" for a better explanation.
I was also wrong about a previous statement whereas you were correct. I was talking about pedal induced Bob and the thread is about overall Bob. I agree with you that the Birdy would have more total bob.
Great talking suspension with you---Have a great weekend---Rick