Sending a requirement for the keeper to identify the driver is normal and reasonable for things like speed camera offences.
In this case, it's reported that the casualty was invited to obtain CCTV footage and when he did, the letter was sent. Some years ago, it was widely reported that investigation of crashes would concentrate on KSI (killed/seriously injured.) I've pointed out before that serious injury is increasingly interpreted as potentially fatal. Perhaps we are edging towards "has received the last rites" or "next of kin have been approached about organ donation."
More to this than meets the eye or perhaps a one-off? Within the last few days:-Possible hit-and-run driver found after mum turns detectivehttps://www.bbc.co.uk/news/uk-england-n ... e-48095667
PS There are other issues here, the most obvious to me - although I didn't think of mentioning sooner - is the effect of the publicity. On the apparently rare occasions when the police act of headcam evidence - they rightly say it should not be published on social media. It can alert the suspect and may affect the possibility of a fair trial. In a more general sense, in a case like the current one it can confirm to the baddies that the authorities are not bothered. Or perhaps some searching questions will be asked about what on earth is going on. Or not.