Remember, this is aimed at employers and open-source projects, not the justice system. Besides, what alternative are you suggesting? Start with the assumption that harassment reports are false, and throw them in the trash?
For example:
We recognize that false reports are very unlikely, but we also recognize there is currently an enormous social bonus awarded to victims of harassment, particularly female victims. Let's examine all the facts, and even if we can't gather enough evidence to take any action, we'll keep a record of this report for any future incidents.
If any corporation used your suggestion as an official statement including the "but we also" segment, they'd be thrashed mercilessly in the media, and for good reason.
Why not just start with: "All complaints will be investigated, and regardless of outcome, records will be kept for future reference."
Particularly in tech, from most to least common:
1. An outpouring of sympathy
2. An outpouring of attention
3. Mobs of angry people ready to fight on your behalf
4. Job offers
5. Conference speaking offers
> they'd be thrashed mercilessly in the media
Yes, they would.
1# All complaints will be investigated
2# All accusation of crimes will be forwarded to the police.
3# All details will be held behind locked doors, including the name/s of the accused and name/s of the accuser.
4# Actions will be taken if policy has been broken, as per a impartial committee that is picked by the community. Actions will also be taken if anyone is found guilty of a crime by the justice system.
Why does this 'rule' applying to organizations make it any different? It is always morally shady (at least, unfair) to assume by default that someone is guilty without any sort of process.
Civil law uses the "balance of probabilities" burden of proof.
A project kicking out a member doesn't have to meet any burden of proof, they just have to show that they're not being discriminatory.