"Even with shade, 40C (104F) is well into heat stroke territory. Thankfully, the couple had enough sense to stay put, in a lean to, near a water supply."

Many people work all day everyday in 40c temps. If water is available, no reason to believe they wouldn't make it.

Helicopters are dangerous, I can see stopping a search due to the risk of the copters hazards over time. But other search techniques would be appropriate, for example using attraction (which the chopper did in this case inadvertently) which can be done with little risk to personnel.