Analyzing Tint Shift in XM-L LED's

Something that bugs me about my warmer XM-L torches is that they have a nasty tint shift to really warm in the hotspot. Both my Zebralight SC600w and Spark SL6-740NW get notably warmer in the hotspot. However, my XENO E03 in neutral white has a very nice, uniform beam. Also, my old ThruNite Neutron Neutral 2A was also very uniform. They were also cooler LEDs.

I took these pictures tonight:

Parallel view of the XM-L in my Zebralight. White balance adjusted to match the tint of the LED. Very even tint.

Off axis view of the same LED showing the uneven tint across the emitter.

The only thing that makes sense to me is that the optical system placed over the emitter is concentrating light making it appear warmer. But, if this is the case, why doesn't it happen on my cooler neutral lights?