Just my personal opinions --
The defect is not common, but not super-rare. I doubt that Bud Jones would have culled it out, even if noticed before shipment. The 2-stage process to fill the purple then black colors was a little off, that's all. It wouldn't add or subtract from value for me as a minor error, but error collector specialists may find it more desirable.

FYI, the $20 Silverbird chip you show was the "key" denomination chip in the series when Bill Borland was selling them originally. The other denominations were much cheaper at the time. I don't know if the differential still holds, but Borland really liked that $20. He had loads of the other chips, but the $20's were used at Baccarat, I think, and the quantity was much lower.

(This is from memory. Check TCR for the latest info.)