Stacked camera sensors have been a thing for a while now; they have improved sensitivity to light by stacking translucent photodiodes on top of each other.
The Nichia 719A is the inverse; translucent LEDs are stacked on top of each other (in a single package) for increased intensity.
Do we know how hard they can really be driven? Zebralight won’t drive them hard of course, but they don’t drive anything else hard either.