While I understand that this behavior went unnoticed for ages and can be seen therefore as unimportant, designating this as documentation bug is quite absurd; perhaps the following wording would be appropriate:

.. note::

    If this function is called multiple times on the same file (in terms of inode; symlink pointing to same file is fine), it will return the module which was first imported via `load_dynamic` instead of the requested module, without reporting any error. The previous call to `load_dynamic` may not be in the same part of the code, but it must happen within the same interpreter instance.