I'm pretty sure that is wrong, actually. If you look in the original source for the information (Jentz: "Tank Combat in North Africa"), the relevant table has an asterisk at this figure, but no mention of why the data is marked that way.
As most sources I've seen quote PzB 38/39 penetration at 100 and 300 meters, I suspect that the asterisk is supposed to mark that this data is not for the 500 meters in the table but for 300 meters. Another thing is that this figure could very well be for 0 degrees as that would seem to correspond with APG tests of the weapon.
However, there is so much conflicting data on this weapon (and other AT-rifles), that it is hard to pin down actual penetration. Jentz doesn't give the source for his information, so it is hard to tell what his data actually represents. It would be very odd if German test data actually exceeded US data for the same weapon!
Claus B