What is the situation for "reproduce a currently-installed system from a list of packages (including version/release if relevant) and a tarball/git checkout/package-deployment/puppet run etc. of configs"?

As far as I know, on most BSDs, unless you happen to have a complete source tree snapshot for said system (becoming more difficult to maintain if you build multiple systems without special tricks to retain binary artifacts), you're out of luck, you'll get today's STABLE or RELEASE, not the one from 17 days ago when your current production box was built that works perfectly unlike the one today that is broken.

This is trivial to accomplish on all Linux distros.

(I would say this kind of issue should be listed in the table in the article).