I talked with several people involved with this decision that tell me the reasons are many:
1) Although they are great for flashlights and room lighting, LEDs are a total pain to implement in spectros. Consistency, spectral drift, and the sourcing of high quality LEDs make them extremely difficult to implement, especially in a handheld instrument. Too many downsides with essentially no upsides. The UV LED in the i1Pro2 is different in this respect.
2) consistency with legacy measurements and best possible inter-model-agreements
3) consistency of high quality M0 measurements over the lifespan of the device
4) the ability to take M0 measurements with a single scan
5) to meet the M0 spec (using anything but tungsten is not recommended by the spec)
6) to create a best of class instrument at an affordable price
7) the combination, flexibility and speed of this design gives them an excellent model moving forward
Their priority is building high precision instruments, and with that in mind, everything clearly points to dual measurement tungsten/UV LED combination.