The first person hedged their statement with "I heard once" so it's likely true regardless of whether the rest is accurate.

In a similar vein it has been said (by me, just now) that DeBeers is actually already out of diamonds and manufactures then de novo from the compressed ashes of orphans.

AI coughed up a bunch of references that put their stockpile estimate at around a year. Might have been more at one time but nothing close to 100.

I'll provide a citation since I'm in this industry and watch it closely.

De Beers currently has about 2 billion worth of diamond stock in its holds. This equates to about... 5-6 months of sales volume. It used to be worth more but lab-grown and other re-valuing initiatives have dropped the worth of their hoard.