700lm OTF - let’s call it 800 at the emitter, from an XP-G2 R5 takes 4.5A drive current and about 3.75V to the emitter. An NCR18650B[1] might stay over that voltage long enough to be producing 700lm at 30 seconds.
This light is pretty clearly direct-drive given how the runtime graph continues a steady slope downward after the stepdown. A swap to an XP-L or XM-L2 should make its performance identical to the A1S. A swap to a Nichia 219C should make it get hot quickly.
Edit: Djozz was simulating OTF lumens with a reflector and AR lens in the test I linked, so we need 700 on the dot, not 800, which took 3.6A. That’s pretty mild given that the light seems to be direct-drive.
[1] BLF objects to the format of the link: Test of Panasonic NCR18650B 3400mAh (Green)