Interactions and conversions between e.g. Point2I and Point2D have always been hard to get right, so it's worth an extra check to make sure they're working as well under pybind11 as they did in Swig. Most important check is to make sure unit test coverage was good; if it was, the pybind11 interface is almost certainly fine.

There may also be some opportunities to enable some interoperability that weren't there before, because I could never get Swig's implicit conversion typemaps working properly.