The idea
The police should not be permitted to refer themselves to their own complaints authority. Complaints should come from and be initiated by police victims or those with complaints against the police. The practice of referring themselves is a conflict of interests and it allows police to frame the compliants and provide the evidence to condemn themselves.
I suspect that self-referral is a case of possible self-justification and added complexity and timewasting.
Why is it important?
All complaints should be made by the complainants and or their representatives. This procedure should follow normal rules for legal proceedings and should be instigated entirely on that basis with full security, confidentiality provided to protect victims and complainants at all times.
Who has ever heard of criminal suspects referring themselves for investigation and prosecution? It is an absurd notion.
So the police should not refer themselves for any criminal or other matters of public interest and concern, but be required to cooperate and provide evidence as from a public body for due investigation by non-political, non-police influenced members of a new authority vetted for competence and independence and appointed for fixed terms.