Hello,
You could well be right!
Jan Horn in his, Euber allen Fronten Chronik des Kampfgeschwaders 6 1941 bis 1945 (2018), alternates between Helmut and Josef. In the narrative and the index he uses Helmut, and in his roll of members of the unit (p.474), - Fw. FF - Delhey - gef am 01.02.1945 - Josef - 1,/KG 6. he uses Josef. In the photographic section at the rear of the book (p.530, photo Delhey), is the following: Angehoerige der 1./KG 6 - Fw Josef Delhey - Flugzuegfuehrer.
The Kracker Database also uses "Josef" -
http://aircrewremembered.com/KrackerDatabase/?q=Delhey
Col.