Why would this OS (or any OS) follow FreeBSD-current ?

This is negative because it just encourages the bad practice on the part of FreeBSD to release 2 or 3 or 4 stable point releases, based on the assumption that "anyone who wants anything should just use -current".

At some point there will be the (absurd) necessity to start bundling a "super current" release because there has to be a test platform, but at the same time everyone is using -current in production and you can't break it too badly.

Or I guess they can just break it badly one of these times and a lot of people get screwed.

There is a deep, deep cultural problem in FreeBSD that just doesn't ever go away and it can be summed up by saying: FreeBSD is an OS by, and for, FreeBSD developers.