The MT09R is an extremely bad example. Those three emitters are driven way beyond the specified operation range and the efficiency and heat output is extreme. Also the MT09R does not really have any fins so significantly less surface area. Maybe 1/3 to 1/4 the surface area of the TR-J20. If you run the emitters within the operation range, the efficiency is much higher and runs much cooler.

A better comparison would be the 9xLED of the ROT66. The head weighs 143.6g and can maintain 1,400 lumens at comfortable temps. Assuming the head of the TR-J20 weighs 1,300g (probably more after I weighed a few different battery tubes that weigh less than I thought), using your analogy it can sustain 12,674 lumens until the batteries run down. The DX80 is also a good comparison since it has alot of emitters and the head probably weighs about 700g would be my guess. The DX80 can sustain 7,000 lumens for 1hr 34mins or as long as the batteries can maintain voltage. Using your analogy, the TR-J20 would equate to at least 14,000 lumens of continuous output. Also both of these lights have no where near as much fins and surface area as the TR-J20. However, the driver in the TR-J20 is probably nowhere near as efficient as these two lights.