I Think He's Embellishing the Rifles History Just a Bit......
The U.S. Army issued a bolt action sniper rifle in W.W.II, the M1903A4 Springfield in .30 (30.06), then they issued the M1C and M1D in cal. .30, then in the '60s and early '70s they issued the M21 which was in 7.62 NATO. The M1s and M21 were semi autos. In about 1989 or 1990 the M24 was fielded which is a bolt action. It's based on the Remington 700 long action and was designed to be convertable by the unit armorer from cal. 7.62 NATO to .300 Winchester Magnum.
The Army didn't have a formal sniper program in 1979. Sniping has been one of those skills that we get out of the footlocker and dust off during wartime and then pack away in peacetime. Even during Vietnam there wasn't an Army level sniper school, but there were unit programs and schools. It was 1989 or 1990 before the Army sniper school at Ft. Benning opened. When I went to 47th Infantry Division (MN, IL, IA National Guard) sniper school in 1988 we were issued mostly M1Ds with Korean War vintage M84 telescopes. There were either 4 or 6 M21s in the school and they went to the left handed firers. (You can't shoot the M1C or M1D left handed because the telescope is offset to the left side to allow for loading the M1 with it's enblock clip) They borrowed sniper rifles from all over the Army to come up with enough to conduct the course.
So I think that the seller is trying to to create an interesting history so that the rifle is more marketable. I don't think any Remington 700s were procured even for competition purposes in 25.06 caliber.
HTH
Jeff