This isn't correct. One example is that URIs don't necessarily provide the means of locating a resource. Another example is that the author says there are no URIs which are URNs.

This is wrong according to the URI RFC, which the author cites: https://datatracker.ietf.org/doc/html/rfc3986#section-1.1.1

   The following example URIs illustrate several URI schemes and
   variations in their common syntax components:

      ftp://ftp.is.co.za/rfc/rfc1808.txt

      http://www.ietf.org/rfc/rfc2396.txt

      ldap://[2001:db8::7]/c=GB?objectClass?one

      mailto:John.Doe@example.com

      news:comp.infosystems.www.servers.unix

      tel:+1-816-555-1212

      telnet://192.0.2.16:80/

      urn:oasis:names:specification:docbook:dtd:xml:4.1.2