It just takes more effort to denonymize. When it comes to laundering illicit funds as opposed to wealthy bankers methods, the point is to break the cash cycle. Monero didnt exist back when I recommended this method, but now that it does and the wallet amounts are not public, COINBASE>MONERO>ELECTRUM>DNM is the best way to obfuscate any connections.
EDIT: Obviously you shouldnt use coinbase, but if you bought them anonymously you wouldnt need to tumble
Stop spreading FUD. Coinbase straight to market is the best safest way. Been doing it for years.