It does not look like there is an option to turn off the auto-login feature. There are several reasons why such an option could be useful:
If a node is unpublished (or otherwise access-restricted), and a user goes to the URL, the first thing they encounter is a weblogin form. This creates the expectation that they are being authorized to access the content. When they subsequently meet with Drupal's "access denied" message, this is not a great user interaction.
Site admins might want to test access control on content without the added layer of complexity that WMD brings.
It does not look like there is an option to turn off the auto-login feature. There are several reasons why such an option could be useful:
Thanks!