Well, you can actually snap the pivot where you want on the mesh as described here: Meshes - Spine User Guide: Transform tools
Although from the video it doesn't look like you dragged it. It seems more like an edge got selected too, but it doesn't look like it from the video. So I'm a little puzzled. In general, the centering seems to be working as it should though.
If you encounter this problem on a different project (our example projects are the best for this) and find it constantly, let us know!
