The LU60A is a Lamp Module - it has a collar adapter to mate with the ScoutLight (or other E-Series body).
The LU60 is a Lamp Module - it has a collar adapter to mate with the Millennium Universal WeaponLight Housing (MH90).
The "M2" bezel is used by the LU60A and LU60, and the M95 and the M2.
The "M2" bezel fits directly onto the G2/G2Z body just like it fits directly onto the 6P/M2 body etc.
It is likely that your G2 threads were ruined either before you attempted to attach the "M2" bezel or as a result of incorrectly screwing it on. Yours is the first time I've heard of this happening. It is likely that SureFire will replace your G2 body if you ask them.
Here is a photo of the G2 with the M2 bezel installed. It works great
The purpose of the LU60A is primarily to allow the ScoutLight to be used as an IR Illumination device. White light LEDs produce practically no IR light so SureFire introduced the LU60A so that the "M2" bezel can use the FM6x BeamFilters - for IR that's the FM63.
The secondary purpose of the LU60A allows the ScoutLight to be used as an incandescent WeaponLight with either the P60 or P61 Lamp Assemblies producing beams that some operators in some situations find to be better than LED white light but still with a more light-weight WeaponLight than an M95 model.
Other applications for the LU60A include using the Black HA "M2" bezel on the Black HA C2 body you may have.
Or, if you have an E2d or E2e (Black HA) you can use the LU60A or just the adapater.
At this point I am not aware of the adapter or the Black HA "M2" bezel used by the LU60A being sold separately.