Yes the full IR is a higher standard - because it is primarily used for public transport, and also a very high degree of precision is needed for flying in airways, and thus poor flying has a substantial impact upon other public transport users. That again doesn't make the IMCR "Mickey Mouse", just appropriate to flying small aeroplanes outside of airways.
I would quote the higher degree of proficiency but also note your comments on currency!
There are PPLs who are just as good and in some cases better than IR holders I know in my own case I used the IMCR in extreme anger in multis and twins OCAS.
But it still comes down to experience. Having flown both ways On an ATP airways and on an IMCR Multi and single OCAS it is far more demanding and requires a lot more pilot interpretation flying with an IMCR OCAS than taking off in CAS cruising in CAS and landing under radar control in CAS.
But that is hard earned experience and surviving that experience rather than the rating which does not prepare a pilot for the precision you quote above.
Hence why I personally promoted the idea of an FAA style IR which is good to go all over Europe.
The worst scenario is neither fully IFR or fully VFR and dumping someone out of the system on their own is the highest risk of all.
A common argument, but a wrong
I cannot agree with that as if the case what level below the full IR would you classify as right? Anything less than the full IR has to be less
Pace