I was thinking the same thing. Even if Will removes the ability for Damus to store an LN address for zaps a user could still put it in a different client. Profile information is stored on relays I believe.
Discussion
Yeah. I feel like their only option to prevent this is to remove the LN thing completely from Damus. And even then like you said all it does is neuter that one client. You still receive it if that LN address is tied to your npub anywhere else.
I'm not really sure what they are trying to achieve other than outright say your app can't allow editing of the LN address section. Or display anything about "zaps"
But that stops nothing.