Nothing is transparent. No one knows who is in the habit of coinjoining their coins, so if a utxo moves after a boating accident, that doesn't mean the boating accident didn't happen. Also no one knows if someone else found the keys after the accident. Also you're perfectly capable of swapping keys with someone physically to anonymize your utxos without an on chain transaction. Absolutely nothing about this is transparent, and this monero guy is mistaken.