@Flick -

Had this assumption that the Unit Tests were a substantial part of the Guidelines.

No worries. :) I don't see the change as especially controversial, to be honest. If a Theme passes all of the code guidelines, there's very little chance, outside of deliberate design decisions, that a Theme would not pass all of the Theme Unit Tests as well - and we've always tried to defer as much as possible to the developer's design aesthetic and decisions.