A site can have one or more site address, and, apparently only defaults to one. The first site address created for the site is always set as the default, but this can be later changed.
To change the default site link, you can follow the steps below:
1. Click the site from the Sites and Templates dashboard.
2. From the Site Details, click Links from the top menu.
3. If you don’t have any other links created yet, click on Create New Link
4. Once you’ve created the new link, click on Change Default Link
5. A box will pop-up, choose from the drop-down menu the new link and Save