From the AAIB report it is clear that, while CC have the authority to order an evacuation, the company policy is that they should only do so in an extreme/catastrophic situation. My airline has similar wording in the manuals.
The situation on that aircraft was clearly not extreme/catastrophic. The flight crew were concious, aware and able to communicate. The cabin crew member acted outside their remit.
In SEP refresher training it is always interesting to ask CC to describe examples of what they consider a catastrophic situation. The answers are often illuminating.