Been to / through the Black Forest many times (well 8 or 9) since 2009, and the reduced speed limits seem to increase each year, went last year for the first time since 2018 and was quite shocked how much of it is now 70kph (44mph) on sections where you could ride any bike around the corners way faster in the wet.
TBH even at the national 100kph limit you needed to speed a little to maintain a nice flow, but getting caught at 70 or 80 in a 60 was going to cost you a few quid, doing 80 in a 40 is likely to become a big problem or very expensive, plus you now potentially have a load of other vehicles in the way travelling a lot slower than you compared to say 10 years ago.
We arrived late PM at the Baden end and got a good run down to Pension Williams (about 25 miles along the route) with very little traffic and no plod, I took it steadier than ever but tried to enjoy the tighter bends (on tha assumption the speed traps would be on the straights between the bends) but it really ruins the fun as you acclerate into a bend and brake coming out of it.
As with all poular roads the authorties have a problem with nutters crashing at 120 mph in a 60 limit and think think the answer is to change the limit to 40mph, as if those who were happy to do 60mph over the old limit will now obey the new one??? As we know all this does is ruin it for the 95% of people who are reasonably sensible and ride / drive within their limits and below speeds where you have no chance of reacting if somethign unexpected happens....,
....we could argue what that speed is forever, but IMHO if there were not such high speed crashes and youtube video's of people doing 130+ along that road we could all go there and ride it at a fair pace and maybe up to @80-90 without too much fear of impending jail time.
IIRC around 2010 bike mags promoted the B500 as a "free Nurburgring", which saw it flooded with UK Power Rangers all desperate to post the fastest video / have the highest speed crash, and I suspect not just the crashes, but the complaints from locals being carved up by these kind of riders, or having their weekend peace shattered by noisy bikes being ridden at high speed.