The only real other circumstance that I can imagine is the fact that it could be an ordinary Model 70 barrel and motion using a alternative XTR inventory. This is certainly not likely although...I suspect that it is as you explain, an unmarked XTR. This gun is chambered in .308 https://win-70-featherweight97520.post-blogs.com/48115415/the-smart-trick-of-winchester-model-70-xtr-featherweight-that-nobody-is-discussing