Man-made diamonds are falling in price and appealing to more people
wsj.com
wsj.com
Not to mention the ridiculous dance where they make methane from the air - I guarantee that is much less green than just buying nat gas or compost gas.
Lab grown diamonds don't fix the core problem - diamonds are mined by slaves, in conditions remarkably similar to Hell. Lab grown diamonds help launder blood diamonds into the general supply. Moissanite has none of those problems, looks nicer than diamonds, and doesn't involve any of the human suffering. It's made by and benefits people like the HN crowd. That seems like a clear winner to me.
You suggest lab grown versions can be used to launder the 'real' ones...to what end? Lab grown versions are considerably cheaper; laundering implies you will mix the two, which will likely reduce what the real ones would fetch. What would be accomplished by laundering beyond a mustache-twirling scheme? How would the alternative be any better at ending human suffering?
I would posit that the exact reason manmade diamonds are rising in popularity is that they're not mined at all. It's better for the environment, for workers, and for the customer paying the bill.