While reading the source code trying to figure out how to configure a custom security context repository, I noted that the 'security-context-repository-ref' attribute ref is not listed in Appendix B. Other attributes are undocumented also; compare the 'ATT_*' constants in HttpConfigurationBuilder with those listed in the documentation.
BTW - this is not a "trivial" defect in my estimation. A trivial documentation defect is a spelling error or some cumbersome text. Any documentation defect that requires the reader to delve into the source code is non-trivial. (OTOH ... if you disagree, perhaps I should stop wasting my time reporting documentation issues.)