Zeffy: you are quite correct; the absence of a warning box should indicate that circling procedures have been constructed using the same criteria as the IAPs. Where it gets more complicated is on the ATC pages, which refer to a shown table which isn’t. I guess that this is simply a formatting issue - or does the circling diagram included later refer to all circling or only where an OCL is presented? More confusing is that in the three decades that I have been operating into Greece, none of the circling heights have, to the best of my memory, been altered on change from OCL to OCH/A. That does not mean that I would not be happy to accept that my original assertion was mistaken.
The definitive answer must of course come from the Helenic AIP. Sadly, I can only find an online version in the Greek language and as nearly forty years has passed since I studied Greek I can offer no more.