i've seen those same #'s and am disppointed by what i see.
the 3cell L6 burned longer than its lil' Luxeon brother the L5 (at least that's what i've read in the product pages for those lights).
if we accept these numbers as accurate, then the drive electronics must be very inefficient bucking the excess voltage, or possibly the G3L starts out brighter, or perhaps (and this could be the case, barring thermal limiting) burns brighter longer before output starts to decline. normally one would expect less current drawn by the drive electronics due to the higher supply voltage with 3cells, resulting in greater burntime (i've measured such when playing around w/various drop-ins. i'm still leaning (wishful thinking???) towards maybe SF is under-guesstimating the burntime, or some aspect of the light's brightness/burntime. haven't seen any burntime plots yet. sorry, i don't have an authoritative answer. size15's, you copy?