Ok, the BLF A6, stock with 5A led, mode 3 of 7, so 100% 7135 controlled and fairly constant:
Bare led: 80.9 lumen
Bare led + white plastic centering ring: 79.7 lumen. So 1.5% loss by the ring
Assembled BLF-A6 with non-AR lens: 67.2 lumen
Assembled BLF-A6 with stock AR-coated lens: 69.1 lumen. So the AR lens gains 2.8%.
So going from the bare led to the assembled stock BLF-A6 with AR-coated lens will cost 14.6% of the light, with non-AR coated lens 17%. Note that the coated lens is 1.5mm, the non-coated lens is 2mm, this will not so much absorb more light but it may cause some extra light loss to the side.
If you calculate back the effect of just the reflector (well, almost, plus loss from the bezel which is as good as completely out of the way in this light), I get 10.3% loss (so 89.7% efficient)
So using this 24mm head tube-style host, in single led form with a reflector it will extract more light (83%) than in triple led form with Carclo triple optic (73%)