You are quite correct that the police don’t pass legislation, but they are required to enforce it. So I’d be surprised if there was much variation of interpretation between police forces, they do have working groups to discuss and decide their approach to legislatory changes.
The thread is about dashcam, and you introduced smart phones in your post at #42, and whether it’s agreed or not hands free devices aren’t illegal. But in certain circumstances using one could still lead to falling foul of the law. A web search should enable you to find the source legislation.
“In 2022, the Government introduced a Statutory Instrument (SI) amending the
Road Vehicles Regulations 1986. This SI effectively introduces a zero-tolerance policy where mobile phones are concerned which means that even the act of simply holding a device will trigger an offence being committed”
Regulation 110 of the Road Vehicles (Construction and Use) Regulations 1986 (S.I. 1986/1078), (“the 1986 Regulations”) prohibit the use, while driving a motor vehicle of hand-held mobile telephones or other interactive communication devices, when performing an interactive communication function.
www.legislation.gov.uk