It was around before the Debian Technical Committee made its decision. It wasn't one of the options to choose from, but it was an existence proof, for those making the decisions, that systemd unit files will not lock them in and that there's a route for Debian packages that have systemd units on Debian kFreeBSD and Debian Hurd.

Too bad it is not the unit files one should worry about, but the continued scope creep of the systemd project.

by the time one want to move from systemd to nosh, or anything more limited in scope, one may have face the rebuilding of Linux user space from the ground up.

It's not the unit files as a potential lock-in that one need worry about now, because of the nosh project. But it most definitely was one thing that people thought about then.