Not sure where this information is coming from but I do not believe it to be accurate. That was not a rifle Remington built, perhaps the AMU did but they built all sorts of science experiments. By the time we (Remington) were affiliated/owned AAC were long past using the AICS 2.0 chassis. The AMU had a full machine shop and built MANY different rifles for a wide variety of events and reasons (sometimes "just because"). Just because they used a M24 action does not make it a "little known variant of the M24". If that is the case there are WAY more to include a variety of calibers out there that others did.
The M24 while being the issue rifle for the US Army and Air Force, it was also sold commercially, to law enforcement and internationally and thus many of them were in the wild. On top of this people have been faking the M24 from the beginning as well. In this case I have no doubt that the AMU got actions from RAC and built some guns for some reason (assuming this is true to begin with).
What are the 2 "tier 1" sniper schools you are referring to? Within the SOF community SOTIC (now the SF sniper school) was/is the only tier 1 sniper school although in the past they have stated that the USMC Scout Sniper instructor course would be considered a similar school. This is not necessarily due to the quality of school (although both are excellent) this has to do with who can work at primarily SOTIC. Each of the SF groups run their own sniper courses generally called "level 2" courses were are typically ~2 weeks or so (I ran them for many years). However, if you want to work at the school house you have to have graduated SOTIC (the level 1 course).
I don't know where the rifle/s depicted above came from but I am pretty certain they didn't come from RAC. I continue to be somewhat surprised and amused at the stuff popping up that supposedly has some provenance and pedigree. To all you potential buyers, ask for proof of any and all claims before spending a pile of money on any rifle.
I am sure the haters are going to come flying out of the woodwork, oh well. If the OP of the above gun personally worked at the AMU and had a hand building it/them then good on you but they are still not M24's, they are custom rifles using M24 actions.