Yeah, in my set up my 4000 K is only getting about 1250 lm. But I barely use turbo either it is just for marketing. I still find it handy though when wanting a big burst of light to view something further away when I've brought the wrong light. Lol.
About the cell. A lithium ion cell has a max continuous discharge rate. You've probably seen it as CDR. What that means, is that the manufacturer is making a claim that that cell should not have a load put on it more than 3 A continuously, if you want it to still be at 80% of the original capacity after 500 full cycles. Or something like that different chemistries and manufacturers have different cycle rates.
It does not mean that the cell cannot put out more than 3 A, just that it is not very good for it in long-term. There will also be a burst discharge rate, which will probably be somewhere around 6 to 7 A for 15 seconds for the cell. But I have not seen a spec sheet for it so I am just giving numbers.
In this case, that poor cell is being hit pretty hard on Turbo. And I don't imagine that if someone used it a lot, it would still be at 80% capacity after 500 cycles. But that's what we sacrifice for power right? Lol.
I have not seen a test done for the particular emitters in this light. But I believe the closest one available from a major manufacturer is the Nichia e17a. That LED requires 2 A to produce 500 lm. Three of them would be 1500 lm and 6 A total. Now I'm not saying the TS10 is the same numbers, as again I don't have a reference for that emitter. And with the electronic tail switch, it would be quite difficult to do a current reading. But I bet it's somewhere between 6 and 8 A