Yondering,
Yeah, I know the 7.62 Creedmoor is the .300 T/C! And the only real difference between the .300 Savage and the .30 T/C is the T/C's slightly longer neck. As another gun writer mentioned (in a private conversation) when the .30 T/C appeared, "Hornady and T/C went to a lot of trouble to reinvent the .300 Savage."
I have also mentioned in print, more than once, that Hornady's claim that the 6.5 Creedmoor is a completely original case design is somewhat questionable. I saw my first 6.5 CM case in 2010,and it reminded me a LOT of the RCBS .250 Savage Improved--which had a 28-degree shoulder. And in my first article on the 6.5 Creedmoor, published that year, I described how to fire-form .22-250 cases to 6.5 Creedmoor with the Cream of Wheat method--which works very well.
An awful lot of "new and completely original" cartridges go back to Charles Newton's .250-3000--and the .300 Savage, which was essentially a follow-up on the same case.
