I tried to do the same research and I'm at your same conclusion. The act of correlate node-id, channel-ids and UTXOs is something neccassary for annaounced channel to avoid antispam. So only channels that prove to be correlated to a real utxo can "sign themself" to the register graph of routing channels.
This seems not the case for anannounched channels, so there seems to be no correlation node-id / utxo for them.
There is still a loss of privacy in giving away node-id (like in the actual implementation bolt11 invoice) cause it risks to make correlations across different payments on lightning network that we will receive, and open to net-analisys.
Bolt12 with blinded paths should solve this problem.
I still could have understood something wrong, so a second confirmation would be appreciated😅