I can't think of any good reason they did this one... certainly won't outrun their own 6.5/300? Like taking a step backwards..... imo
My assumption is they wanted a new 6.5 magnum that would fit in the standard 6 lug mark v action. They just released it in a rifle that is sub-5lbs for back pack hunting. The same rifle in 6.5-300 weatherby is 1lb heavier.