Why is it a terrible argument? People are more likely to use the easier tool. If it's too hard they wont do it. The facts are there on your own github. If you further separated non-custodial LSPs like Phoenix that can see your transactions as well it would be even more obvious.

So are you saying if Lightning wasn't easier to use privately more users wouldn't use it that way? Of course they would!

Do you expect the average user to use PGP to find someones public keys and manually encrypt every time they want to send someone a message? What if I showed them something like Signal and said everything was done for them by default? How popular do you expect each one would be? The answer is glaringly obvious if you're honest.

If Monero was just as hard to use privately as Lightning I would expect the same consequence.