Never understood the why for the M05 Pro. It was so much better to buy the stock kit then add our own selection of upgrades.
If the M06 Pro kit was anything like the M05 Pro, it did not have the "good" upgrades. My guess would be that they did a small run of these kits and sales were too slow to warrant another.
So far all the Pro versions of the current Minis were not a good value IMH0.