Email subject wrongly uses WP_SITEURL instead of WP_HOME

Currently, the emails which are generated by this plugin have this in the Subject field:

WP Updates Notifier: Updates Available @ http://example.com

As far as I can tell, the plugin is using the value of WP_SITEURL to determine the URL to put there in the subject.

Assuming that is correct, I'd like to ask if the plugin can instead use the value of WP_HOME.

The reason is that many people have WordPress installed into a subdirectory (which is supported and documented by the WP Codex). Therefore the value of WP_SITEURL would be something like http://example.com/wordpress, while the value of WP_HOME would be the actual website URL, http://example.com which is the URL that should appear in the subject of these emails.

If someone were to click on the URL in the subject, when it points to the subdirectory location (http://example.com/wordpress), they would get a 404 error because it's an invalid URL.