Not correct. I can't find images online, but I am pretty sure that there is a map at the Ring itself showing the configuration that Bellof drove. Which has a sort of extra loop/corner at the place where the Grand Prix track nowadays connect with the Nordschleife. I believe this was due to the extension/addition of the new track that was being built. It was temporary, as pointed out above as well, but it was there none the less. About 200 meters longer the lap was that Bellof did.
I'm not saying that you're wrong, my friend, but I learned the circuit from the Duke Video 'In Car 956', which was filmed the same weekend that Bellof set the record. I have not seen the video in years, but I certainly do not remember an extra corner or loop in that section.
When you think about the infrastructure in that section of the circuit, towards the end of the little straight (just past the gate for the Industry Pool paddock, before the sharp left of Sabine's Kurve), the circuit passes across a bridge, with a local public road going through the underpass below. That local road has been there since before the original circuit was built in '27, so would they have moved the bridge? I think that bit of the circuit has always been there, which shrinks the scope for any possible differences in the circuit between '83 and today.
There is no guarantee that the following maps are accurate, but this supposedly shows the circuit as of 1982:
https://en.wikipedia...ordschleife.svg
If that was the layout for Bellof in 1983, at the top of Hohenrain - relative to how the circuit is today - he would have had a very tight (<90°) right-hander, then an extra left-hander and an extra right-hander before getting back on today's circuit and crossing that bridge over the public road. That would not have added any distance to the lap but would have slowed him down by several seconds relative to today's circuit. I can't see its happening.
The alternative scenario would in theory be if the link roads to, and the top section of, the GP circuit had been in place in '83, and, instead of turning right at the top of Hohenrain, they entered the link road to the GP circuit, then took a super-tight right onto the top of the GP (Coca-Cola Kurve), anti-clockwise, and then took the other link road back onto the circuit, re-entering before the bridge. That would have added the 200 metres of which you speak but would also have added many seconds to a lap time.
This is supposedly the circuit as of 1983, when Bellof did his 6:11:
https://commons.wiki...rgring-1983.svg
That layout is the same as today.
In 2019 when Timo broke the record, there was no mention of the circuit having been longer for Bellof. Considering that they were both driving for Porsche, and Timo is a humble guy, I would have expected him to say something if the circuit for his lap had been shorter than Bellof's was.
Tbf, I think that the 'extra' 200 metres are just the difference between the full circuit as it is today and the measured distance when the Industry Pool timing beacons are in use.
Btw, I love this little anecdote: in 2019 when Timo broke Bellof's 'unbreakable' record, after he did so one of the first people to call him to offer their congratulations was Stefan Bellof's dad. NOW THAT IS CLASS. 