Is Enhanced Authentication just Authentication?

In the MQTT 5.0 specification, the username and password in the CONNECT packet are referred to as basic authentication, whereas the CONNECT's Authentication Data and the AUTH packet are referred to as Enhanced Authentication.

To simplify things in MQTT-SN we decided to not add username and password fields, as the same effect can be achieved with a SASL PLAIN mechanism in the CONNECT packet. (MQTT ended up with this duplication because 3.1.1 had the username and password fields).

This gives rise to several questions:

1. Should we refer to Enhanced Authentication at all, or just call it Authentication?
2. Does the ClientID in the CONNECT packet count as Authentication in any way?
3. To allow interoperable username/password use, should we specify the contents of the Authentication Method field for this (and all?) SASL mechanisms? (PLAIN, SASL-PLAIN, or what?)