If a language has Suffixaufnahme both in headed and headless NPs at one time and at some later time it has Suffixaufnahme in only one of the two contexts, that context is headless NPs.
Standardized
IF there is Suffixaufnahme both in headed and headless NPs at one time and at some later time there is Suffixaufnahme in only one of the two contexts, THEN that context is headless NPs.
1. Diachronic analogue to G2, here #17.2. In other words: If Suffixaufnahme is lost, it will be lost in headed NPs before headless NPs.