Not all that long ago, the ANO used to include restrictions on certain Class D airspace inside which mandatory compliance with IFR by IMC rating holders was not permitted.
For example, you could legally scrape over the cliffs into Cardiff VFR below a low cloudbase, but you couldn't fly an ILS in IMC.
This was later amended, so that only Class A airways are now off-limits to IMC rating holders; SVFR is permitted in Class A CTRs, but not in airways.
AOPA's point is that it would be entirely up to national airspace authorities, not EASA, to decide whether an Intermediate IR could be used in whichever part of their airspace they see fit. As is currently the case in the UK for the IMC rating.