I have to say that I thought all EU licences had validity in all EU countries. There is an exception that I know of and that is an EU licence gained by exchange with a non EU licence may not be valid in a country that does not have a bilateral exchange agreement with the country of the original licence.
I notice that most EU countries on this map do not require an IDP. I'm quite surprised that they say Belgium requires it. I would have thought only for non EU licences.