I think Selfbuilt’s video review is the pre-production version. The production version is a revised 02 and has a constant-current circuit design for constant output, among others.
Some quick and dirty calculations, please correct me on mistakes: The MT-G2 has a Vf that is about 6.5 V at 4A current (this is my led-current guess in this flashlight), various resistances in the flaslight eat say 0.3V, the driver may eat another 0.1V so two batteries in series must deliver 6.9V under load. A popular Li-ion (Panasonic NCR18650B Protected 3400mAh) under 0.5x4=2A (there are two series, so 2A per serie) load stays over 6.9:2=3.45V for over 50 minutes.
So I'd say yes, a driver can be be had that keeps the light in regulation for quite some time.
I’m not trying to be obtuse, but I must be missing something. Their website doesn’t say anything about changes from the versions Selfbuilt tested. Yes, it lists constant current as a feature, but that doesn’t mean it really has it in the sense the FA01 does, or that the shipping FA02 is going to perform differently from the one Selfbuilt reviewed.
Selfbuilt has replied and he said he has not gotten a production version of this light, so he can’t say about the differences… In his review he said the one he had was an engineering sample, a pre-production version. He further added that if hears anything from the factory, he will post it in his thread of flashlight reviews.