The line guides on the rod are no exception. A conscientious rod maker will take the time & the effort to shape & polish the feet of each guide down to a taper. This makes for a smoother transition of the thread from rod shaft to guide foot. It also allows the guide to sit better on the rod.
While some line guide manufacturers claim to have already shaped the guide feet down to a taper, it is rarely ever good enough for a good wrap. So, I always taper the guide feet down myself.
The photo below shows a line guide foot as it comes from the manufacturer. This is also how they look if & when I form them myself.