We had sunlight on the affected side, local time about 9 am. I do not believe the skin temperature does come into play however.
My understanding is that the heat generated by the running pack would bring the bleed leak sensing loop above the trigger temperature, unless sufficient outside air cooling is made available by means of keeping the slats open.
Also very vaguely the engineers explanation was that the issue would appear with OAT > 34/35 on older, non-modified airframes. Which were the case.
Wouldn't be slats out only be enough to prevent the warning?
I asked the same, picking the exact word from FCOM "slats". With a piece of paper and DSC F/CTL & HYD it is possible to draw a little risk analysis scenario. And I did not like the results. After a simple failure (procedural, human, technical) one could easily get uncommanded/unintended flap 1 deployment.
In general, any disagreement between cockpit switch and the actual position of a moving surface should be avoided unless the A/C is depowered and locking pins are in place.
Yours,
FD.