In section '2.1.3. Differences from Configuring Previous Versions JBoss EAP', there is a typo:

"In cases where FORM authentication is desired as a fallback, the exact value would be SPENGO,FORM."

Where SPENGO, should be SPNEGO.

Reported by Henry Kühl in a comment on the Customer Portal: https://access.redhat.com/documentation/en/red-hat-jboss-enterprise-application-platform/7.0/how-to-set-up-sso-with-kerberos/chapter-2-how-to-set-up-sso-for-jboss-eap-with-kerberos#comment-1072631