Drop-in configuration have higher precedence and will override the main configuration file, which could be used for systemd-timesyncd.
In addition to the "main" configuration file, drop-in configuration snippets are read from /usr/lib/systemd/.conf.d/, /usr/local/lib/systemd/.conf.d/, and /etc/systemd/*.conf.d/.
man timesyncd.conf
Drop-in configuration have higher precedence and will override the main configuration file, which could be used for
systemd-timesyncd
.