FOLOMOV EDC-C4 Super Powerful, Super Compact 1200Lumens at 99 mm length

It sounds crazy, but this 99 mm length-long flashlight can put out up to 1,200 lumens for 2 hours. That’s a whole lot of power in a compact frame. Furthermore, it offers seven different modes, including four brightness settings and three for emergencies and signalling. The included 18650 battery can be easily recharged without hassle: Just pop in the USB cable and charge the flashlight directly through its aerospace-grade aluminum body. You can even charge other devices from the flashlight if you’re in dire need of some power for your smartphone. For protection, the torch is IPX-6 waterproof and 1-meter impact resistant—not to mention it’s got low-voltage warnings and reverse-polarity protection.

2.6ah/2hour=1.3A
1.3A×3.6v=4.7W
1200lm/4.7W=256lm/W

So I guess what you are saying is that a 2600 battery can only put out the claimed 1200 Lumens for 2 hours if the efficiency of the LED plus circuitry is 256 Lumens per Watt, which is completely unrealistic, right?

What is realistic, maybe 1/3 of that?
I remember reading in another thread that 100lm/W is impressive.