UK police pilots are required to carry out mandatory regular instrument training with a safety pilot on board (whether holding a full IR or not), so that in the event of inadvertant entry to IMC they should be fully competent to recover to a diversion airfield for an instrument approach or at the very least for a letdown to VCF over a safe area.
Why would the CAA not require a full IF rating for such operations if the intent is to provide an Instrumented Qualified Pilot?
I guess another way of phrasing the question would be why would the same CAA insist on an IF rating if there is no "intent" for a VFR operation to convert to an IFR operation.
As to your final paragraph....here in the USA...as mentioned dozens of times in the past by mulitiple posters....we operate on the "You Can unless prohibited"....as compared to the UK "You Cannot unless specifically authorized" mindset under the Air Regulations.
The CAA and FAA rules sometimes defy commonsense and logic it seems!