Nothing in this post is specific to passkeys; it reads like advice to not encrypt data. There’s no way to prevent some users from losing their encryption key anyway. Whatever warnings you include, even when software doesn't connect to the internet and just encrypts local files, someone will write to support that they forgot their password and ask you to "reset" it.
Good advice at the end, though.
The issue I think is that passkey managers don’t make it clear that deleting a passkey can cause permanent data loss
There's a big difference between being kept in the dark and being informed but careless.