If you go on some YouTube sites as my husband does relating to arguments between police officers and members of the public who do actually know the law and film encounters You'd be slack jawed.
I wouldn't. But I've known a fucktonne of police over the years. Which is why I don't have the fawning respect of people who like the idea of the police because they assume they will never be on the wrong end of them.
And because there are some thick as mince officers, who genuinely don't comprehend the law around, the more cynical can get away with it too.
However (see: teachers) the tsunami of revisions every working day make it impossible to keep up. So impossible that it can only be by design.