Well I'm glad I posted this. Fascinating subject, no?
As near as I can figure the Hofner's neck was not glued to the body at the heel in the traditional manner. Rather, they left a small gap, with the neck being attached between the fretboard and the front of the body. This would seem to be a rather delicate situation in terms of sturdiness, but after 40 years it's still his main bass! Seems like it would've been a hell of a lot easier to just put a couple of strap pins on though.