I have been doing a bit of reading and here is some more info/background that I found.

Originally the 6.5 Grendel was invented and released back in 2004 by Alexander Arms. From it's inception until late 2011, a full seven years, it was a non SAAMI cartridge that fell under Alexander Arms proprietary design restrictions. This means if people wanted to make something for a 6.5 Grendel, they had to work with Alexander Arms. Also consumers were stuck with one choice for the most part (at that time).

Seven years is a long time to spend as a proprietary round with only one company acting as the boss over the entire caliber.

On the other hand, from DAY ONE, the 6 ARC came out of the gate as an already SAAMI spec'ed round that other manufacturers can pick up on and use for design etc. In this regard it's sort of like MLOK. It was designed by magpul of course, but in a way it's semi sort of open source. In order to obtain SAAMI specs they have to give up trademarks so it can be a 'standardized' cartridge.

Basically from a business standpoint these two could not have been treated any differently. They were business wise polar opposites. Alexander Arms for good or bad, by trying to control the show stunted that cartridge's growth.