Why? Well the launch, unpatched version of The Witcher 3: Wild Hunt had an unlocked frame rate, meaning the game ran at whatever the system could handle at a resolution of 900p. Subsequent patches locked the frame rate at 30fps. Any Xbox One copy of The Witcher 3: Complete Edition will have those patches, so you need an original version.
According to NX Gamer, the game runs at 60fps in most scenarios, dipping down in the city of Novigrad, where it reaches 40fps. However, you'd be playing an unpatched version of the game, without any of the additional fixes and tweaks CD Projekt Red brought to later releases. It's an interesting test case, but if you're fighting this hard for 60fps, perhaps it's just better to go for the PC version?
The Witcher 3: Wild Hunt patch offering Xbox One X enhancements is still forthcoming. According to CD Projekt Red, it's leaning more on the visual side than the performance side.
"With the additional power of the Xbox One X, we are able to deliver The Witcher 3: Wild Hunt in 4K, while providing numerous visual tweaks such as higher-quality shadows, ambient occlusion & texture filtering, as well as higher resolution textures, and an all-around performance boost," Witcher 3 development lead Jakub Kutrzuba told Xbox Wire. "When enhancing the game for Xbox One X, we wanted to use the additional power of the console to deliver an even more visually stunning experience. When playing the game on Xbox One X, The Witcher 3: Wild Hunt's visuals are sharper and the overall presentation more vivid than ever before on Xbox."