> Why was the decision taken to put these into /usr/lib/systemd instead of
> /usr/libexec/systemd/?
That's a Fedoraism. Why would one put something there?
/usr/lib/ is where private arch-dependent package stuff goes. What's
the rationale for /usr/libexec/ though?
I am not aware of it being a Fedoraism. It is at least also used/populated on an Ubuntu server I use and documented as part of the filesystem hierarchy (hier(7)): https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s07.html#ftn.idm236091914528
