That's not how it works. If your amp is putting our 100 watts, and those 100 watts are all getting dumped into your cab, your cab will be at full volume. The only way to reduce the volume in your cab is to have something else take part of the power. That "something else" is the attenuator.If I understand correctly, the load of an attenuator only works when volume is reduced to zero. At any other setting of volume reduction, the load of the attenuator is not working. The cab will take the load. Am I right?
Whenever you have a reduction in volume, the attenuator is involved.