That's a different matter because there is a meaningful difference between an XM-L and an XM-L2, particularly when it comes to efficiency.
Only about 10-20%. I doubt most people could tell the difference in brightness.
There is no meaningful difference between a flashlight with a perfectly centered emitter and a slightly off-center one.
Yes, and as I already stated, I have no idea if this particular example has any impact on performance. But I don't blame him for checking. It's not a cheap light, and he should expect well-centered LEDs. He should try it out and see if it affects performance, but, how would he know if he doesn't have another unit to compare it against? The hot spot may be too large if one of the LEDs is off center, but how would he know this, and how would he check what real impact it has on throw?
If the LED is off-center, he doesn't really have a way of verifying its impact on performance of the light. All he can do is ask if it's off-center, and if it is, he then has to decide what he wants to do about it. Like I said, I wouldn't bother returning it (unless it's
really obvious there's a problem), but others may have higher standards than me. With an expensive light, it's okay to have high standards.