In the Token Introspection Endpoint documentation (here) we indicate that when “The token was issued to a different client than is making this request”, it should be “considered an ‘inactive’ token”.
However, I create two clients (for instance, ClientCredentialsONE and ClientCredentialsTWO), and I can introspect the tokens issued by the first providing the credentials of the second client just fine.
By the way, the official Introspection Endpoint specs (RFC 7662) doesn’t indicate anything regarding this, but it seems on practice most providers (I’ve tried with Curity, Azure AD and Keycloak) allow introspecting tokens issued to a different client, just as Okta does in practice, so it might be just a matter of updating the Token Introspection Endpoint documentation.