Webauthn AuthenticatorAttestationResponse “getPublicKey” returns a restricted object?

I’m trying to implement passkeys for my web app according to these guides, and I’m primarily working on the registration flow. After I’ve created the passkey using navigator.credential.create, I try obtaining the newly generated public key using the getPublicKey method on the returned response attribute. However, when I try inspecting the object, my browser says:

Restricted { }

According to MDN, this object should be an ArrayBuffer. In order to send it to the server I try to convert it to a base64-encoded string, however whenever I try to do something with this, the browser throws an error saying I can’t access this object.

I’ve already worked around this by sending the attestationObject to the server and having the server decode it, but according to everything I’ve read, I should be able to do this client-side. Am I missing something obvious, or is this expected behavior?