Interesting thread.
In Canada there is only 1 helicopter IR.
One can do it all in a Robbie or Bell 206, there is no twin requirement. The only twin IFR requirement is for the issuance of an ATP-H.
Most people over here do about 20 hours IPT, 20 hours in a Cessna 172 type aeroplane
And do another 5 hours in a Bell 206 and then to an IFR ride.
The Bell 206 is not approved for IFR in Canada because most of them are not equipped with SAS. Therefore if you can demonstrate that you can fly IFR in an aircraft that doesn’t meet the stability requirements then in theory flying a real IFR helicopter shouldn’t be a problem.
In reality the initial IR is just to get the job, anywhere you got to fly IFR for real will require a PPC on a Twin and a PPC is an IFR ride; plus you will be spending quite a bit of time as an FO.
I don’t understand the pre-occupation in Europe with the twin IFR helicopter rating. It must be a throw back to fixed wing where an engine failure while intercepting the LOC can be a handful with the asymmetric thrust, and feathering the {wrong} prop to deal with. That same scenario in a Twin helicopter is no big panic.
When I did IR training(for type rating) I preferred a candidate with an IR on an aeroplane twin than a candidate with an IR helicopter done on a Bell 206. The reason, simply; they were better and it made my job easier.
If I was running the helicopter world it wouldn’t matter what you did your IR on whether it be a single aeroplane or twin helicopter, the PPC is still the catch all for standards.