Because they do not understand what PVC is.
They think it is the PVC causing the damage.
PVC alone causes no damage. It is a very hard material whose chemical structure is only altered by heat.
It is only the chemicals which are mixed with it to produce flexible materials that cause damage.

Polyethylene is naturally softer and therefore more suitable for use without chemical additives to soften it.
However, there is no guarantee whatsoever that either this or any other 'non-PVC' product is free from damaging chemicals either.
If you look at museum archival materials, they are described as 'acid free' or 'chemical softener free'. As long as that is true it does not matter whether the material is PVC or anything else.

Your chip would have bled onto any flip, or onto the chip next to it if stacked for long enough.
That is as a result of the lead red oxide die in the clay coloring and nothing to do with the flip.