That was back then.
Today, lights from other manufacturers can output 900 lumens on 14500 and still run on AA if needed. There's a pretty huge difference between 400 lumens and 900 lumens. Not supporting and allowing for better output on 14500 is one feature that makes Zebralight inferior to the competition.
I believe this is a bit of unsupported handwaving, and I'd like to explore it.
First of all, I want to reiterate what I have already posted, that Li-ion in an SC5 is superfluous, not because ZL could not design a driver that is capable of more lumens with Li-ion, but that by now we have a predictive model of behavior from ZL, and that model of their ideology clearly favors consistency in their driver interface across the product models. This is not a bad idea, and their success is admirable, as having consistent interface and consistent brightnesses and
consistency everywhere you look at their products is unmatched in the industry, as far as I'm aware. In this regard, ZebraLight seems to stand alone.
Your post doesn't offer any competition for ZebraLight by name for direct comparison. Regarding specifically the SC5 stepdown from Turbo, there is only so much one can expect from an Eneloop, amazing and beloved as they are. I am unaware of any other light by any other maker that has achieved 500+lm output from an AA cell
and has regulated constant brightness of that 500+lm before the Turbo steps down. Most other competition that I am aware of may breach 500lm with an AA cell, but the brightness only stays there for seconds, dimming immediately. After three minutes, when SC5 steps down, there is no other AA light from other makers that is even close to 500lm. And this is usually true of the dual chem models, that while the higher voltage cell gives higher lumens, the lumen output doesn't stay put, and starts dropping immediately, and as you point out, often they also have step down after a few minutes.
I'm sure some members remember when vinhnguyen54 got his hands on the SC600 w/ XHP35, and everyone was expecting he would do what he always does, make a light 4 to 10 times brighter. I believe he has had success with another ZebraLight model in increasing voltage and output, but in that particular thread, while he was successful getting inside of the ZL (which is no small triumph), he only praised ZL design and engineering, and in the end,
decided he couldn't make it brighter enough to make it worth offering the mod.
I think this last point stands in stark contrast to your suggestion that ZebraLight is inferior for not offering Li-ion in their SC5 models, and your unsupported inferrence ("That was back then") that anyone else could do better, or is doing better today. ZebraLight isn't holding back, and Vinh's experience supports this: they are cutting edge. And it is clear other manufacturers are not putting any emphasis on consistency of interface or regulated constant brightness of the modes across their models. If the competition has a model that accepts both chemistries, the modes and brightness levels are not consistent between the chemistries nor their other models. And many of them are not doing anything much of note even with Li-ion drivers, but often still lack advancements standard in ZebraLight such as low voltage protection for their Li-ion models.
If you want a flashlight that takes both chems, has no low voltage protection nor regulated output nor interface consistency, and stays in a mode without stepdown no matter the state of your cell, along with the heat effects and eventual damage to its own driver, I bet you don't have to look too hard to find them, nor pay too much to own them.
That isn't ZebraLight's bag. They are doing something else, and it still isn't clear at all, because you offer no examples, that ZL is inferior for leaving Li-ion support out of the SC5. Let's see these superior duel chemistry competitors to the SC5, then we can decide if they are in fact superior, or just cheap crap, which is my suspicion.