No.
The low voltage light will be unable to supply 3a to the emitter (assuming xm-l/l2).
A single 18650 would have to be extremely poor to not be able to supply 3a to an emitter, as said two will not even break a sweat.
Also keep in mind what was said above, the 3400mah cells do sag pretty hard even at 3a, they’ll still light the emitter but not at full output.
I personally find I get longer regulated time out of 2800mah sanyos than I do from the 3400mah panasonics, just because they hold voltage up better under load.
My personal favorites for runtime vs output ar the ncr18650pd or pf cells, although these see much more use in ecigs than torches due to their high current capability.
Basically, as said above, if you stick to Panasonic/samsung/sanyo/lg cells you will not go far wrong, I also do not believe in the light you are using you will see any difference between any cells from any of the above manufacturers, your only going to see any difference when you go to really high output high vf emitters and very high output driver’s. Thats when you need to start worrying about sticking to 20r’s or mnke cells.
If runtime is a real issue, get something like a trustfire a8 or one of the clones, build it up with a 2.6a ld25 driver (the lower load is not noticeable visually but is very noticed when it comes to runtime) and run it on a good 26650 like a king kong, the difference in runtime really is noticeable whilst the difference in size is not.