One of the commenters on Electrek points to this:

"Panasonic's existing panels have low temperature coefficient, so their performance doesn't drop off as much with heat. If they also add in Tesla's Silevo technology which has even lower temperature coefficient, most of the hit for thermals would be negated as compared to standard panels."

I'm sure this is throughly tested, in any case. Panels like these have been in use for a while in Japan.