Utter claptrap. Lots of people drive their track day vehicles to and from the circuit.
There was an incident in Germany some years ago when a round of the World Rally series was stopped because the rally cars did not have TUV approval for all the rally mods when driving the road sections between the stages.
No WRC event ever returned to Germany....rallying all but died in Germany.
So there is a precedent for German police to inspect the certification of parts used upon motor vehicles.
In the UK most track day vehicles are driven to the circuits and are road legal.
As a complete aside I competed in the last competitive road rally in the UK....in the middle of the night in East Anglia we pretty much ignored all road regs....I was driving a 280 hp Escort 2,2.1 BDG,Cibie lights with massive range,flat across x-roads.....the police decided enough was enough,they put a speed trap on one of the long straights,I was clocked at 143 mph and I wasn't the quickest.
They got us all together at the finish hotel and stated that whilst such events were historically based,it could continue no more,they didn't prosecute us but stated that at the next event 70 mph would be enforced.....overnight road rallying on public roads was finished.
I only state this because there are precedents that the police will take action if a line is crossed and they are given instructions from on high to stop an activity which has become a nuisance.
KudosDave