There are 3 XML emitters in that light. You can over drive them. I have a custom single XML light that does slightly over 1000 OTF lumens (verified). That said, that light is most likely crap and the seller is stretching the truth (to put it politely).
They say it is 3800 lumens which is total
. The best that thing could do OTF is about 2100 lumens (which I'm sure it is nowhere near) if they don't over drive the emitter. Knowing how they under-drve the emitters in all the cheapo lights, use inefficient drivers, and use cheap lenses, I am guessing 1500 OTF lumens tops.
Will the shady ebay sellers never end?