I'd rather have chalk than waxes leaching out from old discs. A ChemE told me that calcium carbonate is used in minor amounts (<15% by weight) to stiffen and stabilize polypropylene blends.
All my older Discraft Z stuff (early/mid 2000s) has developed spiderweb cracks throughout. Discs just crumble. Haven't seen this in any other plastics from the era.
Innova & Millennium CE from that era has aged the same way. Goes to show manufacturers were (and likely still are) getting plastic from the same sources.