Certain Variables won't expand in Windows System Environment Variables PATH

For some reason there are certain Environment Variables that won't expand when used in the "PATH" variable in the System Variables.

For example, %SystemRoot% works just fine while %WinDir% doesn't. %ProgramFiles% and %ProgramFiles(x86)% doesn't work either.

Obviously I know that I could just use the full path rather than a variable but that's not the point.

Any ideas?

Here is a screenshot/example: