In the chapter "2.1.3.3. Securing a Classic WAR Application" in the step 3 there's stated:

Add the /WEB-INF/keycloak.json file to your Red Hat Single Sign-On configuration

This is a bit misleading. You are not placing any config file to RH-SSO. You are placing a new keycloak.json to /WEB-INF of the secured WAR application.

Proposed change (similar to EAP adapter):

The first thing you must do is create a keycloak.json adapter configuration file within the WEB-INF directory of your WAR.