Mother Ducker 1.00:1 ratio reduces gain?

When creating a makeshift de-esser contraption with a Mother Ducker, AIR Kill EQ, AIR Noise Gate, send/return and a submix, I noticed that Mother Ducker still reduces gain even with "1.00:1" Ratio. Did I do something wrong, is that "by design", or is it a bug? Since the Mother Ducker is (AFAIK) the only sidechain-capable compressor available inside the MPC, it would be preferable to have a wide range of controls.

(A multiband compressor/expander/gate like Ableton's Multiband Dynamics would help as well, and why not have the Mother Ducker BUSes available as actual general purpose buses...)