The discrepancy you're observing between the Unity inspector preview and the Spine preview window is a known issue. The Unity inspector preview for Spine assets uses the Spine Runtime to render animations, which should ideally match the runtime behavior in your game. However, there are some limitations and differences in how Unity's editor API handles these previews, especially when using Mecanim.
The preview window in Unity does not use Mecanim under the hood; it uses the Spine Runtime directly. This means that while the preview should be similar to what you see in the Spine editor, there can still be differences due to how Unity handles animation states and transitions. The jerky interpolation you're seeing might be due to these differences or specific settings in your Unity project.
For the most accurate representation of your animations, it's recommended to test them in Play mode within Unity. This way, you can see how the animations will behave in the actual game environment, including any transitions and blending that might not be accurately represented in the preview window.
For more detailed troubleshooting, you might want to check if the issue persists with different SkeletonDataAssets or if there are any specific settings in your project that could be affecting the animation playback.
