Though some sort of reversing
Though some sort of reversing noise is necessary in an EV/Hybrid, there is no reason why it needs to be different to the VESS 'engine' noise that these cars make when going forward. That has been good enough for ICE vehicles for 100+ years.
The pitched bonging noises or 'angelic voices' are antisocial as they carry too far for the job they are supposed to do. My Kia Niro can be heard reversing from 100 yds away, with windows in the house shut! They have also been shown in several academic studies to be ineffective at actually warning pedestrians in typical spaces such as shopping mall car parks. This is because pitched sounds do not carry such good directional information to the human ear as more broadband sounds (like an ICE engine). Governments have been very slow in legislating effectively about these nuisances but I hope to see pitched reversing 'bongs' being banned in Europe soon.