为什么Windows不检查相对路径文件夹的存在？

Refer to the example below:

$path = "C:/Program Files (x86)/Apache2.2/cgi-bin/myapp/sessiondata_xxx/session_xxx_/../../code/doc/memo/index.csp";
var_dump(is_file($path), realpath($path));

Notes: The folder sessiondata_xxx and session_xxx_ do not exits.

On Windows, the output is:

TRUE, "C:/Program Files (x86)/Apache2.2/cgi-bin/myapp/code/doc/memo/index.csp"

On Linux, the output is

False, False

So, my question is: Why Windows does not check exists of folders for the relative path?

Thank you in advance.