The current documentation forshutil implies that all copy functions benefit from fast kernel-space copying on Windows via theCopyFile2 API. However,shutil.copyfile() is an exception — it still uses a userspace read/write loop.

This PR clarifies that:

• shutil.copy(),copy2(),copytree(), andmove() useCopyFile2 (when available)
• shutil.copyfile() doesnot, and remains a buffered userspace copy
• Provides practical guidance: prefercopy2() overcopyfile() for better performance on Windows when metadata preservation is acceptable

The change has been verified by:

• Building the docs locally withmake html (0 warnings)
• Confirming the rendered HTML displays the updated text correctly

Related toGH-142407.

📚 Documentation preview 📚:https://cpython-previews--144354.org.readthedocs.build/