`locations` and `resource` parameters requirements

resource
Currently, spec recommends to use the resource parameter when placing a authorization request (PAR or not), when
a) scope is being used &
b) > If the Credential Issuer metadata contains an authorization_servers property,

locations
Similarly, spec requires to include it in the authorization_details again when authorization_servers is present.

To my understanding both of those parameters make sense when the credential issuer is not acting an authorization server.

Given that nothing prevents an issuer (which acts also as an authorization server) from populating the authorization_servers with its own - single - issuer id, I think that the requirements could be better expressed by simply stating that
resource is recommended and locations is required only when credential issuer is not acting as an authorization server and remove the reference to the authorization_servers attribute.

Start by reading the linked OpenID4VCI sections on using the scope parameter and authorization details, focusing on the conditions involving authorization_servers, resource, and locations. Compare those requirements with the issuer also acting as an authorization server. Done means the specification text clearly expresses the intended conditions without ambiguity.