Is the WordPress URL autocomplete feature bad for SEO?

We asked John Mueller from Google Zurich to tell us whether it could be a problem that WordPress autocompletes URLs when they were partial. For example: when you type http://domain.tld/my-ra and when the URL of your WordPress post is  http://domain.tld/my-rabbit/, WordPress automatically does a 301 redirect from http://domain.tld/my-ra to http://domain.tld/my-rabbit/

The response from John Mueller was:

That’s a pretty awesome way to redirect broken links to your right pages, I don’t see any downside to that.

Comment from discussion henriduf’s comment from discussion "I am John Mueller, Webmaster Trends Analyst at Google. AMA.".

Unfortunately, there is an issue behind the auto-complete feature of WordPress.

By the past, the French version of sitecozy was https://sitecozy.com/fr/ and this URL has been deleted. Because of the auto-complete feature of WordPress and since the said URL started with fr, it automatically redirected to https://sitecozy.com/free-forum-platforms-vs-paid-forum-platforms/

The content of those two pages was tremendously different: One was in French, the other one was in English. In this case, the 301 redirect does not match with the idea of a 301 redirect according to Google. According to Google, a 301 redirect should be a 1 to 1 page. The two pages should be similar. I know that people get residual google juice from other URLs to one URL this way. Disabling auto-complete means losing some residual google juice.

How to disable the auto complete feature from WordPress, add in a plugin or in functions.php:

function remove_redirect_guess_404_permalink( $redirect_url ) {    if ( is_404() )        return false;    return $redirect_url;}add_filter( 'redirect_canonical', 'remove_redirect_guess_404_permalink' );

You can also install a plugin that contains the code above:

Disable URL Autocorrect Guessing

Following the question we posted on reddit we saw a new issue related to the auto-complete feature from wordpress.

In a log, we found that googlebot followed a strange redirection. It was something like that:
http://mydomain.com/best-teas-for-healing/”>tex to http://mydomain.com/how-to-switch-your-tyre/ 

The two URLs had no keyword and no subject in common. We deactivated all the Htaccess redirects and the Redirection plugin redirects. Nothing changed then, in a plugin. We added the remove_action that we mentioned above. Guess what? The first URL then returned a 404 error page. This means that the auto-complete went crazy and redirected to a page that has nothing in common with the original URL.

For you information, there is a debate about this issue