In your analogy, the keyserver is a phone book. You can find keys there, and yes you can try to use them, but it's not like telling someone you can be contacted

In your analogy, the keyserver is a phone book. You can find keys there, and yes you can try to use them, but it's not like telling someone you can be contacted on a particular phone number, but rather like them digging through a phone book and finding your name in there, possibly for an unused landline that you technically own but isn't wired up - who knows. Telling you to use a particular phone number - say through a business card, a contact page or a profile - is the analogy matching configuration of your domain to publish your intent, similar to how your domain also specify where you mail server is.