Earlier quoted context omitted.
I have trouble imagining truly complete anonymity being helpful. This is an invitation to abuse the system. Abuse could result from personal conflicts and office politics, or even people who wish to undermine the system itself by entering bad data.
The point of an anonymous system is to encourage people to speak up without a first-mover problem, because in every case of ongoing sexual harassment there is never just 1 victim - it's always a pattern of behavior. Someone receiving exactly 1 report is probably not a problem. Someone who accumulates reports continuously as team members change probably is .
No. If the system is truly anonymous, then people outside the team can submit reports. Continuous accumulation would not indicate there is probably a problem with the accused, given the motive and opportunities for abuse of the reporting system.
Elsewhere in this thread the difference between anonymous and private is discussed, along with semi-anonymizing strategies for achieving privacy protection, which I believe would be helpful for the outcome you describe.