Partial truth, partial cover up ?
Since decades there are serious speculations about high-ranking spies in the OKW general staff. Several generals in the Eastern Front planned their own offensives, without interference from the General staff, often referred to as the "Spy Nest" by people like von Manstein. Some say Martin Bormann was a Russian spy. Maybe this enigma stuff is made up to create a smoke screen.
This kind of leakage is sort of detectable by smart people, they will notice when "by coincidence" the enemy seems to be on the right place at the right time each time something happens.
It is however unclear why German counter intelligence was so bad, the incredible losses in the U-boat war, was a clear sign something was off, since Oceans are big, and they seem to be spot on all the time.