Wrong Category Still Works

Has anyone noticed this behavior: as long as the name of the post is correct in the url, it doesn’t matter if the category is wrong–it will still redirect to the correct page.

For example, I have a post in category widgets. My url is:
http://www.mydomain.com/widgets/redwidget.html

(yes, I know I don’t need .html in the url, but humor me.)

So if I type this url into my browser:
http://www.mydomain.com/blah/redwidget.html

it redirects and changes the url in the browser to
http://www.mydomain.com/widgets/redwidget.html

Has it always done this and I just never noticed? I’ve been trying to Google information about it but haven’t found it mentioned anywhere.

Thanks, Susie