Additionally, according to
https://www.airmen.dk/p327.htm Spreckels was at Aalborg May-June '44 to help convert bomber pilots to fly fighters.
This could suggest Spreckels was recognised as a competent instructor and maybe accounts for the large gaps between claims, if he was heavily involved with Ausbildungsstaffel/JG 11 during 1943-44?
Its a bit like clutching at straws, but who knows.....