Just fyi, issue appears related to non-instantiated template services - i.e. the below contruct:
SYSTEMD_SERVICE:${BPN} = "${BPN}@.service"
which in the past was not an issue for the rootfs creation.
It may have been an "undocumented feature" so far, and I guess such services in fact should be disabled (SYSTEMD_AUTO_ENABLE = "disable"). At least, doing so enables the rootfs to succeed.
Thanks