knowing where the money goes is the same on xmr and LN, because it's possibly not the final destination.

So he can say "aha! This is the xmr output!" But it's used as decoy, or real spend, later, so since there's no utxo set you can't see where outputs are "sitting" or if they ever moved. His analysis is useless.

Meanwhile he'd say "aha! That node is not my LN node it was a proxy!" Which is the exact same as where the output "is sent to" but doesn't "end up at". So by that logic every xmr output is a proxy output, while not every LN payment is a proxy, which makes xmr more private by default