Specifically the conspiracy theory that passkeys are some kind of backdoor is strange to me:

For intelligence agencies, and for corporations like Microsoft, Google, Apple, Facebook, Amazon – giving you convenience and security is likely not their primary goal. I think they have an entirely ulterior motive. They can use passkeys to prevent you from running unapproved software.

And:

I’m not one to argue about slippery slopes, so I won’t claim that the campaigns to protect children online today will tomorrow turn into laws designed to make it easy to identify political dissidents. But I will say that the widespread adoption of the passkey technology being advertised to you as convenient and secure is capable of permitting such laws to be easily enforced.

The ulterior motives are really around cost of managing credentials and having better assurance that a user is who they claim to be. Instead of paying to have a help desk or a password reset service they can offset the cost to you to have the necessary computing modules or hardware keys to authenticate. Passkeys will fall out favor quick when the major governments have the digital IDs deployed en masse. And there are better and more effective means to achieve the other ends the author is worried about, like having a monopoly on 96% of web browsers or killing the market for PCs.