Hum, I am not sure if I agree, jon_slider 
According to this thread (Sofirn HS10 emitter swap - #12 by Verodin):
but that is something that doesn’t happen with the Fenix.
The Fenix has a pressed bezel (not screwed in) + o-ring + lens + optic + PCB.
And the optic has 3 very short legs, unlike the one from HS10, which is flat in the bottom.
Also, in the photo below, it can be seen that the “egde” in the Fenix, where the optic sits, is lower than in the HS10, making a tight fit and provoking contact between the optic and the PCB.
While there seens to be a gap between PCB and optic in the HS10, in the Fenix they are in contact.
The screw that the Fenix has is to keep the PCB in place to prevent it from rotating (not lifting), since the driver has no retaining ring (it is just “fit and glued” to a small rim inside the head structure) and could rotate freely and tear the wires.
