Python 3.6 installation doesn't add launcher to PATH

[ChrisW]

The installation guidelines for Python 3.6 say:

"Per-user installations of Python do not add the launcher to PATH unless the option was selected on installation." (https://docs.python.org/3/using/windows.html#from-the-command-line).

However, I've installed Python 3.6 with the 'include PATH' checkbox ticked for my user only, and although C:\Windows\py.exe exists, it has not been added to my PATH. 

I also tried installing for all users, and this also doesn't add it to the PATH.

Is this a bug, or have I done something wrong?!