For example, if Confluence is accessed for the first time at https://www.example.com/confluence, the baseUrl will be set to https://www.example.com:443/confluence.

When the baseUrl is looked up from the request (such as during set up, or during an upgrade), Confluence puts an unnecessary port 443 in the URL if it starts with https. Port 443 is the standard port for HTTPS, so should be removed.