AOG - "Then if he was with a police car on his tail would have been the more serious offence and surely he would have been charged with that offence."
The report doesn't say that the police car was 'on his tail', it said that the police car was the next vehicle to pass along the road - the offending car could have been out of sight by then.
I have driven for forty-two years in all sorts of conditions, I have never splashed a pedestrian, ever - it is quite easy to slow down if you are driving at an appropriate speed for rain in a built-up area.
No one is suggesting the drive should slam on his breaks, or do a Starskey-and-Hutch style swerve, just slow down and pass through the puddle slowly - it's simple courtesy.
Failing to be aware of conditions and other road users is Careless Driving, so the offender is - as the saying goes - bang to rights.