What it is not
Timestamping does not prevent anybody from willfully preparing and then submitting false information.
However, it allows crystal-clear identification of after-the fact manipulations:
It prevents the researcher from retroactively suppressing measurements not supporting his pet theory or the accountant from changing his books to hide his embezzlement.
To achieve a trustworthy process, other means like trust, control, and double-checking at the time of data entry still need to be in place.