Why does a language undress? Strange cases in Indonesia

I have argued in various presentations that it is inherent to natural grammars to maintain a considerable level of complexity over time: simplifications occur, but are counterbalanced by complexifications due to grammaticalization, reanalysis, and new patterns created by phonetic erosion. I argue that only extensive acquisition by adults makes grammars simplify to a significant overall degree. Creoles are the extreme case, but languages like English, Mandarin Chinese, Persian, and Indonesian are less complex than their sister languages to a degree that correlates with their extensive histories of non-native acquisition at certain points on their timelines. In this paper I address a few cases in Indonesia that challenge my stipulation. The grammatical simplicity of Riau Indonesian and the languages of East Timor is due to adult acquisition. Meanwhile, a few completely analytic languages on Flores suggest either that my stipulation must be taken as a tendency, or that we can take the nature of the languages as spurs for investigating sociological disruption in the past.