Book: How to Set Up SSO with Kerberos
Revision: n_2419309_how-to-set-up-sso-with-kerberos_version_7.1.Alpha_edition_1.0_release_0-revision_8279967
Section: 1.3.2. JBoss Negotiation

Add explicit information JBoss Negotiation is used for legacy security and is not necessary for elytron.

Something like:
"JBoss Negotiation is a framework that ships with JBoss EAP that provides an authenticator and JAAS login module to support SPNEGO by legacy security solution in JBoss EAP"