They know that Belloq wasn't German, right?
Also, to respond to Koosh's post, I really, really can't stand all the revisionist crap that came into the Indy-verse post-"Crusade", including the usage of "Dr. Henry Jones" everywhere.
Even if that's Indy's "real name", he was NOT USING IT professionally, at the very least prior to "Crusade."
One could argue that, afterwards, he decided to go back to alternating names once he patched things up with his dad.
It wasn't like, "Hey, my name's Henry, but my close pals call me Indy."
He was using Indiana Jones in EVERY capacity, personally and professionally.
The government thought that was his name, his universities thought that was his name. Chattar Lal heard that name "at Oxford", even his old friend Sallah had never heard of it before.
Grrrr.