I don’t think that Anduril is optimized for Li Ion voltages (3.6 - 4.2v) per se. It’s just that the rest of the driver often is. Buck, FET, and Linear (7135) drivers rely on the battery voltage being just slightly higher than the LED’s forward voltage. Buck drivers step down the voltage, and Linear burn the excess as heat. Otherwise, you need a boost driver to increase the voltage. Driver Types.
You could DIY StaticX57’s Anduril Candle for 2xCR123a or 1xCR123a, but it would require redesigning the power path.