If you create a file in your home directory that you give permission to anyone to read or write to, having a+x on your home directory will actually allow them to read/write the file if they know the full path to it.
This behavior is useful on subdirs, too; for example, a shell account I used in the past had http://server.example.com/~username/ mapped to /home/username/public_html, and since the webserver ran under a user that didn't have root permissions, making /home/username a+x allowed the webserver user to access the files that I wanted to share over the web (assuming I had public_html chmodded properly, of course).
So it's less about cd and more about direct file and/or directory access for purposes of widely-accessible files.
This behavior is useful on subdirs, too; for example, a shell account I used in the past had http://server.example.com/~username/ mapped to /home/username/public_html, and since the webserver ran under a user that didn't have root permissions, making /home/username a+x allowed the webserver user to access the files that I wanted to share over the web (assuming I had public_html chmodded properly, of course).
So it's less about cd and more about direct file and/or directory access for purposes of widely-accessible files.