If, on the other hand, you're talking about normal tanks, then the answer is indeed no. That's because, for non-armored equipment, the DF factor actually affects the survivability of the equipment against AP. But, for armored equipment, the survivability is set by its armor thickness. The Defense Strength of armored equipment is just a display value to give the player an idea of how tough the equipment is to kill. It has to be derived from the armor thickness.
I've been looking at the manual a lot on this recently and just wanted to confirm my understanding:
A unit is either armoured or not. (Armoured checkbox is ticked or not).
If it is armoured, then any fire at is uses the armour penentration rules set out in the rulebook (a roll to hit based on targeting level and terrain/environment, followed by a roll to penetrate based on the ratio of armour penetration to thickness). The defence stat is not relevant (and as you've described the game 'helpfully' adjusts it)
If it is not armoured, then any fire at it uses the ratio of anti-personnel to defence ratio to determine success. There is no rule to hit or to penetrate. (Does anyone know what the formula used here is?) The armour stat is not relevant.
When firing, a unit will make either an anti-personnel or anti-armour shot. The game engine attempts to have the units with the highest armour piercing rating target the enemies with the highest armour rating, with a bit of randomness.
I've seen it implied that the Infantry tag somehow contradicts the Armor tag i.e. you cannot have Infantry and Armor on the same unit (or if you try, it malfunctions somehow). Is this the case and if so does it apply to cavalry?
The manual says the Agile tag reduces the chance of the target being hit. Does this apply to both kinds of fire?
And ... what does the Shock Cavalry tag do? Any ideas at all? :)