From that link,
Class F. IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive flight information service if requested.
Now that I don't have a problem with, as you say its almost what we do in G.
But, "air traffic advisory service" is (my bold)
Air Traffic Advisory Service is a service provided within advisory airspace to ensure separation, insofar as practical, between aircraft which are operating on IFR flight plans.
What does that mean to me as an ATC? I am required separate, even though you are not subject to a clearance, unless I can't, in which case I'm not? "Ensure" and "Separate" have very very specific meanings in our books, and neither allow for "if practical" escape clauses. (It may be that Eurocontrol are using the terms more loosely.)
Some people have argued that out "G plus" is a temporary, transitional airspace category between our old full service OCTA and proper ICAO G, but the transition has lasted 20+ years and counting.
And it looks like I have started an airspace classification argument, sorry
