When I got my Mk4, it had what looked to me to be the original spare tyre, and it was easy to see by the sheen of the tyre, that it was fit for nothing.
I guess it means we should use spare as working tyre, otherwise you end up have £100 of tyre not earning it's keep and being thrown away.
Also good to lift out the spare every 6 months to check no moisture build up on the alloy, as it does mark them.
I tend to find in the winter chucking soaking coats in the boot can soak into the boot may and then condense on the wheel, so my spare has slight spots on it from this (as well as the time when it had the dreaded boot leak before I bought it)