Someone was asking earlier about use of pax stairs to get the passengers off the aircraft,
It's possible to have an 'evacuation' using stairs, however from the photos this appears to me to be a textbook QF 'precautionary disembarkation'.
The flight crew no doubt were in communication with fire services who advised them of the circumstances outside the a/c and the PIC having this information at hand would decide the best course of action.
A full evacuation using slides is a risky business often resulting in injury (eg broken bones) to pax and crew and therefore is a last resort. If you have ARFF in attendance and nothing is actually on fire then it is probably safer for the majority to expedite disembarkation via stairs rather than popping slides.
Having said that please note that QF cabin crew are trained that during precautionary disembarkation, it can become a full evac at any time. In which case any and all available doors with slides would be used. Correct any doors with stairs in position would continue to be used with stairs.
Also note in this case I highly doubt any of the CC would have used any of the LHS exits, as evidenced by the photos of No 1 still running.
Hope this helps. Sorry for the slight thread drift but I hate seeing the suggestion that by not using slides they did something 'wrong'
