At the end of the page (see PR URL) in Example 7.4. Flavor Specific PKGNAME there is sentence As all packages must have a different package name, flavors must change theirs, using flavor_PKGNAMESUFFIX and flavor_PKGNAMESUFFIX makes this easy That sentence contains flavor_PKGNAMESUFFIX twice and flavor_PKGNAMEPREFIX is missing.
A commit references this bug: Author: mat Date: Fri Feb 9 17:19:22 UTC 2018 New revision: 51411 URL: https://svnweb.freebsd.org/changeset/doc/51411 Log: Typo. PR: 225691 Reported by: knezour weboutsourcing cz Sponsored by: Absolight Changes: head/en_US.ISO8859-1/books/porters-handbook/flavors/chapter.xml