I have heard the Tatra ban story before and the more I think about it the less likely it gets. I don't think any car was more dangerous than combat. The Tatra required a different driving technique but was not more dangerous than other cars if handled correctly. Officers with cars in that class had trained drivers. And Germany could not afford to discard any form of motorised transport.
I suppose it was possible they were instructed not to drive themselves but always be chauffeured by a trained driver.
I would be willing to bet large sums of money that you are correct! As we all know, the NAZI's kept all of Hitler's orders in triplicate, that's why it was so easy to prosecute them. Still, a fun old wives tail. And yes, I would love to have one of these cars, after all, Leno has one.