Similar but not same here ion RUT360 with RUT36X_R_00.07.01.2:
When only LTE is connected on boot ntpclient does not set time, not even after manual /etc/init.d/ntpclient reload.
Initially after boot ntpclient is not found in ps output.
After manual reload a ntpclient process is running. When i run that same command from shell manually the time is updated.