LiFePO4 has low capacity, its main advantages are higher reliability and ability to handle high current, LiFePO4 isn’t new, it already existed back in 2012, that product it will be useful for some people but for most flashlight uses 3.7V/4.2V Li-Ion is superior. The ones in the link have a capacity of 450mA @ 3.2V = 1.44Wh, a good 3.7V 16340 may have 3.2Wh, an 18650 may have over 12Wh
Edit: added 18650 comparison, fixed typos.