XPIDL, scriptable Interface Func Args using not scriptable type

Firefox Development
#1

the nsIWebAuthnService using not scriptable interface, nsIWebAuthnRegisterPromise and nsIWebAuthnSignPromise
Is this the intended thing?

https://searchfox.org/mozilla-central/source/dom/webauthn/nsIWebAuthnService.idl#37
https://searchfox.org/mozilla-central/source/dom/webauthn/nsIWebAuthnPromise.idl#10

#2

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