Again some bored blogger had nothing to do and went with this clickbait-ish headline!
The reason for the stat showing but also misleading millionaire numbers going up is pretty simple, there were around point around ~36000 addresses with a balance between 50BTC + a few satoshi, most of them being from old blocks that have been mined and never moved.
Once bitcoin passed back over 20k, those addresses become richer than 1 million, but it's highly probable that there aren't 30 000 new millionaires but more like in the thousand if not hundred since a ton of those coins are most likely lost, and quite a few should belong to the same individual, Satoshi!
Well, you do have a good point, but still, I don't think there is anything wrong in having those addresses added as new bitcoin millionaires, as long as the amount of bitcoin contained In the wallet have reached the worth of a million dollar or more..
Whether those wallets, and bitcoins In it be lost forever, is up to their respective owners, for we the on-lookers, there is no way to be 100 percent sure that those bitcoins are no longer accessible to their owners, but as long as they remain on the richlist and holds bitcoin worth millions in dollars, it is completely normal to give them the millionaire title.