4th Edition DF chart - Opportunity Fire question

[Juiceman]

Had occasion to pause today as I read this thread again. In Section 1.2 of the 4th Edition Rules, the definition of "Armor Value" states that "Motorized vehicles without a printed armor value have an armor value of -1 (usually trucks and jeeps)". So, technically, this indicates that trucks have an armor value, albeit -1. The Direct Fire Table, 4th Ed., indicates that an "M" check refers to "All units without armor values in target hex check morale (14.1)". So, if the definition of an armor value is in play, trucks would not check morale unless an "X" were rolled, in which case "All other units in hex must make an M2 morale check". Is one correct in assuming that DF will only affect a loaded truck if an "X" result is rolled? Or do players just use the  DF table as though the truck did not have any armor value for protection?

1.2 Definitions

Armored Fighting Vehicle (AFV): Any unit with a printed armor defense value (even a value of 0). This includes self-propelled artillery, armored cars, special armored engineering vehicles, armored personnel carriers, and other similar vehicles. A tank leader may activate any of these.

Armor Value: A vehicle’s ability to resist enemy Anti-Tank Fire. A unit’s armor value is printed in the lower right corner of the unit’s playing piece in yellow on a burgundy
field; higher numbers are better. Motorized vehicles without a printed armor value have an armor value of -1 (usually trucks and jeeps).

A Truck is not considered an AFV since it does not have a printed armor value and the -1 value is for AT Fire Only, to make trucks more venerable to such fire.  

A truck or jeep should not be considered having armor on the BF or the DF tables, unless it has a printed armor value on the counter of at least 0.

7.25 Armor Immunity.
If a unit has a printed armor value (even a value of 0), it
is immune to all but an X or #X result on the direct fire or
bombardment fire tables. If the unit is an APC, any unit or
leader it’s transporting is immune as well. Armor gives no
protection on the Assault Table (for example, M = Morale
Check for all assault targets including all AFVs).