Yes, that is how it works… if it’s not a user, then how else would my plugin know who the guest visitor is to show them their own clear links? It simply stores a user ID for the matching user, or whomever is logged in at the time (when no matching user).
Not much I can do about your specific situation as there is no way for me to track these guests/visitors safely, unless you want them to create logins and passwords, in which case, that’s what a WordPress user account is for. =)