Did some testing. Same Vessel Interaction makes no difference at all with the legs.
However, I got some more luck when I strutted the bottom hinge on the piston part to the leg. By turning up the traverse rate and turning off damping on the truss' hinge, I could use the piston to make a difference on the landing legs, but only when gravity was hacked in the debug menu to a level similar to the Mun. For reference, I tried to recreate the setup seen in the screenshots, but the piston part was attached to the fuel tank.