The dock is centered, yes, but the inspiration for the Start button and menu is the Apple menu, which has always been at the top right of the main screen, in the menu bar. You can even hide the dock completely if you want to. The dock also re-sizes dynamically and doesn't go edge to edge even if you only have a single item in it. You can also stick the dock to one side of the screen and have it vertical if you want.
I have been a Mac user since 1987, so I know the history of the interface, and I use Windows when necessary and have used it since Windows 3.0 and used DOS before that.