I do not think that the tailplane necessarily has to push down for the decalage to exist!
No one was discussing the stall case. In normal straight and level the tail-plane must produce a down force because the C of G is in front of the C of P causing a nose down moment.
The Main Plane does stall before the tail. However, the tail is a different surface with a different plan form, aspect ratio and aerofoil. It won't therefore necessarliy (or even probably) stall at the same AoA as the wing.
Obviously if the main wing is at AoA of +6 degrees and tailplane is at 3 degree angle to tailplane, the tailplane is providing some lift,
This could only happen if the C of G was behind the C of P, in which case the aircraft would be divergently unstable in Pitch,