Police Ops in the USA are not Public Transport.
The FAA classifies them as "Public Use" and do not regulate those Operations.
Part 135 which covers "Air Taxi Operations" also does not require Twin Engined Helicopters.
The UK attitude, be it formed by the CAA or other political interests, is unique to the UK and now EASA I guess.
The question is whether that attitude is founded upon Science or mere Whim.
I seem to recall a couple of Twins landing in downtown London and in Glasgow that killed people on the ground.
Explain that away to me will you?
How does a second engine in both those crashes figure into the death and injuries that were caused?
You guys over there are way too much into the Nanny State Mentality!