I presume that you are using a Cookiebot scanner, which you already mentioned, to identify the cookies. It happens so that the scanner tends to identify the externalReferrer cookie even though it is not there. Could you please check if the cookie appears when you visit a website and check the network tab with a list of cookies in the developers console?
Here is an article on how to check cookies manually: How to Check Cookies on Your Website Manually - CookieYes
A similar thread: Analytics without a cookie banner (EU GDPR compliant)