Please explain your comment for the rest is us. Was that a sarcastic "it really happened because it made it to the chain" or a "we'll never know whether value was exchanged from one person to another because the owner of both wallets could be the same person" - or both, neither or?

Commenter said "there's no way to distinguish fake wash trades from real ones" and I showed a case where a wash trade was, to anybody looking at it, very obviously fake.

I agree with the other part of the comment. Blockchains do not track "persons" but "wallets" and so metrics like "number of users" will not be accurate. But it is not accurate to imply that it is impossible to recognize wash trades. In many cases they are very obvious, and even can be automatically flagged. In other cases - like with CEX mixers - only the authorities can detect the fraud.

OP probably meant fake wash trades and real non-wash trade ones, not fake and nonfake wash trades

The flash loan trade was a wash trade, obviously “fake.” Other wash trades are also - very often - obvious because the blockchain is transparent and easily analizable.

How can we tell that the buyer and the seller are two different people in real life?