I believe thats specifically pistol grip radios with air escs that often require the pistix- I have no issues with my laser 6 and the MMM V1, and I have seen someone with a DX6 in their TXT-1 too (
clicky, 3:30 onwards is the good stuff) with a novak SuperRooster esc. Not exactly a conventional setup, but I do want a multi-channel stick radio, and the price on the dx6i isnt much more than a new laser 6 either- so much more you can adjust justifys the layout I reckon.