MOR reduction by (Air) Interdiction

[Wiedrock]

12.1.4. ADJUStING UNIt MoRALE to NAtIoNAL MoRALE
Individual units may have different morale levels to the
current National Morale level. This can be due to the
morale allocated to the unit when it first enters the game.
For example, some of the units that will be transferred
from the Soviet Far East in late 1941 will have a higher
morale to reflect their elite status and experience gained
in the various clashes with the Japanese up to 1939.
Equally units will gain or lose morale as they win or lose
battles (23.10.4).
Ground unit morale may decrease due to losing battles,
suffering from air interdiction, or being in an isolated state.
The higher a unit’s morale is over its national morale, the
greater the chance the morale will be reduced when it
loses a battle.
Retreated units may lose one morale point, which will
be increased to a loss of two morale points if the leader
Morale check fails.
Routed units lose one additional morale point.

I am trying to figure out how this is supposed to work.
MOR reductions for Axis in 1943+ when the NM decreases should (how I read this) allow a reduction of unit MOR by Air Interdiction. The MOR otherwise basically can only be lowered by Germans losing battles.
But somehow I do not see MOR reductions happen due to Air Interdiction!

Any ideas?

[Wiedrock]

After 5 turns of constant Interdiction there is still not a single MOR point lost.

[Joel Billings]

Not sure, but interdiction is a carry over from WitW. I seem to recall it had two effects, one you could suffer damage to equipment moving through an interdicted hex (but I don't remember if you get it when you enter or when you leave the hex). 2nd, if you are in combat and the unit's hex has interdiction on it, you would suffer some automatic disruption at the beginning of the combat (again from memory).