You are to modify the older LM465 before they completely redesigned them with a surface mounted controller and 5 volt power supplies? The ones with no supply regulation and 5 volts goes down from the added current driving the triac as you change the brightness.
The momentary mode for the appliance module works because of its design. It has no memory of if it is On or Off. So if you send it an On and it is On already it used a sensor to determine if it needed the relay pulsed. When you take the sensor off the output. It thinks it is Off and will pulse a few time to try and turn it On before giving up.
Lamp modules don't have that type of electronics and maybe why trying to momentary it will not work.
The new CFL friendly Appliance modules are also a completely new design. New surface mounted IC and electronics to go with it. Not sure if the momentary mods work for those either.