Yes to the name origin, but not the other bit according to David Emary. In a quite detailed feature article on the cartridge's origins and design features in the Lyman Long Range Precision Rifle Reloading Handbook published in 2018 Mr Emary confirms the widely known story that Dennis Demille pushed for a new cartridge at an after matches dinner, actually a three-way discussion between Messrs Emary, Demille and Joe Thielen, Hornady's head engineer for cartridge case production at the conclusion of the 2006 CMP Service Rifle matches. To quote David Emary:
"Dennis said that he was getting really frustrated with his Tubb 2000 match rifle and the 6XC cartridge it was chambered in. I asked him what problems he was having and got an earful. To boil down a lot of conversation there was no standardized loading data for the 6XC. Most of the loads being used were quite warm in order to get the performance needed to be competitive at longer ranges. He reported frequent hard bolt lift and pierced primers, both of which could be very problematic in the rapid fire matches. Dennis stated he wanted a cartridge that was very accurate, was not loaded to problematic pressures, would have a load that would produce moderate recoil at 300 yards for rapid fire, would be as good as anything to 1,000 yards and had to go in a short action receiver. He also wanted this ammunition to be factory loaded, accurate enough to be competitive and have the loads written on the label so anyone could produce them. In short he didn't have the time to reload and really didn't want to. At first glance this seems a pretty tall order, especially the performance expectation from a factory loaded round. We concluded the conversation with me throwing an idea at him for a 6.5mm cartridge to which he responded, 'I don't care what it is as long as it works.' I had my marching orders."
I'm not disputing that Dennis Demille had previously used the 260 Rem in one form or other, but it's obvious from this description that his immediately previous cartridge was the 6XC, and there appears to be no automatic expectation on his part of a 260 Rem based design being a front-runner in finding a replacement. (In fact, the Creedmoor design uses Hornady's existing .30 TC cartridge case more or less unchanged except for necking it down to 6.5mm. David Kiff of PT&G who had been closely involved in the earlier development of the TC wrote in a different thread on this forum some years back that it had originally been intended for the 30TC to be the first of a 'family' based on the case as are the 243, 260 etc, etc on the basic 308 Win and he designed a 6.5TC chamber as part of his original brief, the various Creedmoor updates and tweaks being in effect to produce a match variant of that never introduced hunting design.)