It's a matter of the " focal length " of your lenses and the 3 element uses...... ( 3 elements ) to effect a longer focal length, however there are losses due to edge clipping of the beam, the G8 is a single element with a longer focal length and less losses even with the higher divergence of the nubm0e compared to say....a ndb7875, this is why I mentioned the 3X beam expander, it lets you focus tighter at longer distance.
The G2 is a shorter focal length single element AR coated lens and is very efficient, IINM it's 2.35mm FL
The 3-element is somewhere around 5mm EFL and around 70% efficient with the diodes natural divergence also being a factor.
The G8 is 8mm FL
There is EFL and BFL ( effective focal length ) and ( back focal length ) but lets not concern ourselves with that as it's not a big factor in what were doing here, for our practical purposes the 3 most common lenses are G2 = short, 3E = medium, G8 = long
It's a shame that you might have had a freak laser diode that's extra strong but had to remove the protective lens-can, it would have been a good one for the Chinese to re-capped with a window can and protective gas back-fill, I may order again another nubm0e re-canned and test it, however I'm not expecting it to be like what you describe, 9W through a 3-element would mean 12W through a G2.....yet that's not the result you got.........so something in your testing doesn't add up, because the G2 is 95% efficient while the best 3-element is no more than 70% efficient.