Maybe never. When the XP-G came out over a year ago, it was immediately available in a R5 bin. Except for a few S2's and S3's that only seemed to be available to a couple of manufacturers (and will be gone soon), the higher bins never came.
Well, the S2's weren't THAT great, in the main producer of them, 4Sevens. The tint bin they got access to was very green. The only decent S2 torches were the Christmas ITP set, which is also useful. (USB rechargable 18650 torch+Awesome keychain light+solar charger with built in batteries AND flashlight? Yes please.) They were a yellow white.
More green in the output will inflate the lumen rating due to the eye's sensitivity to green, which lumen measurement is biased towards. It doesn't surprise me that this tint is common among the highest bin emitters. If they're barely making it into that bin, it becomes more likely that the tint is what tips the scale.
I suspect the same frill, also the filter of cheap light meters are 'biased' , before got my lightmeter I performed several measures with a solar panel which give readings of incandescents bulbs accord the lumen flux state for the manufacturer in comparison with white leds of knowing flux, when test the same incandescent with the light meter the readings are lower by much, almost a third or less..
Ι have bought many U2 from cutter and LCK, both are better than T6 binned leds, and the performance is mixed, some LCK U2 are better than Cutters' leds, but some cutters' U2 are better than LCK U2 too. As for the color, can't really tell the difference, both are white!!!
Supposedly there are several U2 lights out already, the cyclone C88 claims to be a U2 light, and the U2 bin has been on cree datasheets for some time now.
If only there was a way for us to tell which bin our XM-Ls are.
It just goes to show that you use the forum's past post to learn from. Perhaps you found this during a search or just got carried away when looking for interesting posts. It happens to everybody that doesn't only lok at the recent posts.