From the mail it doesn’t exactly look like “upstream dependencies on systemd” but rather like a lack of features in sysvinit:

The second reason for dropping System V is that packages like GNOME and soon KDE’s Plasma are building in requirements that require capabilities in systemd that are not in System V. This could potentially be worked around with another init system like OpenRC, but beyond the transition process it still does not address the ongoing workload problem.

So it seems a bit like sysvinit is simply a dead end and there is definitively not enough manpower for a transition to openrc/elogind/whatever…and it’s a good chance to consolidate the exiting workforce on a single version. Sounds all pretty reasonable to me. But it can’t really serve as example for systemd being an absolute requirement even for LFS now and them being “forced” to use it.