Excuse my French, but that is total nonsense. Not a single controller (other than the UK CAA) needs to practice the use of an VDF and the corresponding phraseology. Every other R&D facility in Europe only needs the occasional radio check.
Facilitating another free frequency would also not be impossible. In stead indeed half of west Europe is being bothered with the GA pilot who blocks the emergency frequency for 5 minutes. The risk is that after practice pan number 5 you forget to turn up the volume of the emergency frequency again with bigger consequences.
UK CAA R/T in general is very non standard compared to ICAO, and this is not a complement. I don't understand why they think they know it better that the rest of the world.