Hi,

Yes, this is by design. If you change the document name on the Form tab, you only change the name visible in content tree and as it will appear on live site in the menu. If you want to change the URL, please go to the document Properties tab -> General -> Document URL path. (In version 4.0 is this setting moved to section URLs right under the General item).

The alias path is not changed and it is unique for each document (it is one of the identifiers by which you can distinguish the document).

Best Regards,
Juraj Ondrus