Apologies if I misled anyone.
My comment was based on my experience when I needed to undertake an IMC renewall a couple of years back.
There were no twin rated IMC examiners available at the airfield I wanted to continue using, most had decided to give up their rating due to the JAR regs, even though JAR doesn't cover the IMC rating.
It was not suggested that I could do it on a single and still be valid on a twin, although that is what I did at times in the distant past.