No, yes.  systemd_system_unitdir is newer so it's used less.

Ross

On Wed, 18 Aug 2021 at 08:48, Robert P. J. Day [off-list ref] wrote:

  i've (so far) run across a small number of OE recipes that use the
identifier "${D}${systemd_unitdir}/system", which appears(?) to be
equivalent to "${D}${systemd_system_unitdir}". is there any potential
functional difference, or should this be standardized?

rday