Not quite correct. The problem is the lubricant they used to put on the copper cores prior to the pvc jacket was slightly hygroscopic and therefore it was the moisture leaching out of the lubricant."Green Goo", in household electrics has been attributed to a plasticizer within the pvc sheathing leaching out.
This plasticizer reacts with copper.
(I think the cables are made better nowadays.)
Although nothing to do with cars, household PVC cabling deteriorates if it touches polystyrene cavity insulation.
They tried with French chalk but that doesn't stick well to single core copper conductors so is more suited to stranded cores.
They now tend to use a silcon based lubricant.
(the reason for the lubricant is to stop the pvc sticking to the hot copper when the vacuum draws it down. It'd be a bugger to strip without the lube.)
Innuendo anyone?