My man, you are an optimist!
Yes, SF could be using some other emitters, ...including SST-50 for 900L.
Correction for you: XR-E EZ1000 has a 0.98x0.98mm die, of which ALL of my SureFires are and all those those I have seen are, so I'm still waiting to see SF is using the smaller EZ900 anywhere. They may be, but who has seen one?
The R3 I used is an HEW. R4 are rumored, but I have never seen one for sale (I typically shop Cutter for Cree) have any of the Chinese mfgrs even claimed to use the R4 XP-E? That happens many months before mainstream mfgr use it. And the R4 over R3 gain is only 7%. Take away the generous assumptions I put in those calculations and the lumens are still not up to those claimed by SF, or very marginal. And if the 250L LX2 is XP-E, then it makes the 500L LX2 Ultra an XP-G (due to the same lux at twice the lumens and same optic meaning the LED die is twice the area), which it can not be even at S2 bin. So the chain fails.
Now you are assuming the 900L light uses XM-L. Do they? Has anyone received a 900L Surefire and taken it apart? Running th numbers, 990 emitter lumens (XM-L at 3A) could become 900L with 90% eff, but again that is assuming 25C, which the emitter will not be at time of FL1 lumen measurement. Then no window losses either. Close enough to be possible though. With top bins, top efficiency, etc. Lot of ifs. We will find out when the 2012s are taken apart what LEDs are being used and if Surefire is diving LEDs to max spec, which the runtimes seem to be indicating, but that would be a new MO for them. Only time will tell. I plan to get one of the programmable lights as soon as they come out. Either an EB1 or LX2, whichever comes out first. And it will be about a day before I take it apart unless somebody else beats me to it.