In the current world an "email address" is not solely (or sometimes even primarily) for delivering email, but rather an identity or username for various systems

In the current world an "email address" is not solely (or sometimes even primarily) for delivering email, but rather an identity or username for various systems, such as for signing git commits. So a key linked to an identity (email address) does not imply in any way that this key is also used or usable for encrypted communication.