When I was instructing full-time 6 years ago, I was told by one of the D+D controllers that they wanted practice pans for training some of their junior controllers.
Recently monitoring 121.5 on box 2 in MAN area. listened to GA aircraft genuinely lost. Poor guy couldn't see his airfield despite being vectored virtually overhead and sounded v unsure of himself. I wonder how he felt to hear the occasional voice say "You're on Guard" (US accents mainly). It was annoying to hear so-called professional pilots not actually listen to the transmissions and keep their gobs shut. It's filed as a difference by the UK and published as such. If operating to HAJ or DUS (and probably plenty of other German airfields) the plates say there is uncontrolled VFR traffic up to FL100. That's not ideal either but you read the relevant notes and take heed.
Regards