Effect of rubble and mines on local supply?

[Mowgli]

Im my recent Scheldt '44 match, I started to wonder about rubble and mines and how they affect local supply. 
I ran some tests in the scenario 1016 Venraij and the results left me somewhat confused: 

RUBBLE

1) If you control a road INTO a rubble hex, local supply seems to be totally unaffected by rubble (this seems to disagree with the manual which states that roads cannot be used into/out of (?) rubble hexes). 
2) If you do not control a road into a rubble hex, then rubble does affect your local supply (movement cost for the virtual supply trucks = terrain x 3)

However, I could not completely explain what happened. I was observing the village of Brabander (hex 17.13). As long as I controlled the road in 18.12, the local supply in Brabander/rubble was 53 - basically the same as in surrounding hexes, telling me that the rubble had no effect at all. Without control of the road access into Brabander, however, the supply plummeted by -10 to 43%. I would only have expected a drop of 7%:

village (30 for motorized) 
* 4 (motorized in mud) 
* 3 (rubble) 
* 0.02 (2% supply calculation) 
= 7.2

MINES

In the same scenario, I also noticed that clearing an already penetrated minefield increased my local supply (beyond the minefield) by 5%. So it seems as if a penetrated minefield does allow supply to pass through, but still affects it somehow?

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What are your experiences? Is this all working as intended?