That's funny, I did LFS a few years ago and specifically chose the systemd version so I could better understand it. I don't think this is a huge deal, I believe the older versions of the document that include SysVinit will still be available for a long time to come, and people who want it will figure out how to muddle through. If at some point in the future things diverge to such a point where that that becomes untenable, someone will step up and document how it is to be accomplished.
Didn't you find though that systemd was just a black box? I was hoping to learn more about it as well- and I did manage to get a fully baked LFS CLI system up and running, and it was just like "ok install systemd..." and now... it just goes.
Sysv at least gave you a peak under the covers when you used it, and while it may have given people headaches and lacked some functionality, was IMHO simple to understand. Of course the entire spaghetti of scripts was hard to understand in terms of making sense of all the dependencies, but it felt a lot less like magic than systemd does.
This decision means that no testing of SysVinit will be done in future LFS and BLFS versions. The onus will be on the experimenter each time, but my hope is that a body of advice and best practices will accumulate online in lieu of having a ''works out of the book'' SysVinit solution.