From what I have seen in this thread, the 45mm stainless parts are narrower than the 46mm body. So the 45mm band in inset on a 46mm, and the 46mm is too wide for a 45mm. It sticks out noticeably on the edges.
I haven't noticed this. All my 45mm bands have fit perfectly flush with my new 46mm Series 10. I believe the connectors are the same size as before.