I very much agree with the spirit of this tweet, but in terms of 'quality' would that not come down to their intended use? by that I mean don't industrial diamonds look quite different than their natural made counterparts and are valued strictly for their practical use such as machine parts and tools?

If we were talking Jewelry, which is more about cosmetics/symbol of status than anything else, that changes quite a bit.

I think diamonds my be a poor example to use in this case.