Mathematically, the intersection of a line with a surface is a line.

But the current behavior of intersected is always to return a surface:

Returns a path which is the intersection of this path's fill area and p's fill area

To the very least, an optional parameter should allow to get an open path.

This would allow to clip an open path inside a rectangle, such as:

clipped_line = line.intersected(rect)

Here is a concrete use case, with workarounds, from another user:

https://stackoverflow.com/q/8759864/3565696