I dont know mate, if we talk about Sundanese, since the East Asian feature usually mostly found in Bandung City, cold and high ground city, so maybe they develop that similarity from the climate for long period of time and then spread over other areas in West Java. But, Palembang people are known to be inhabited by Chinese immigrant since Srivijaya Kingdom, it is a recorded history. My friends from Palembang really looks like Chinese though
But some tribe in Kalimantan island is actually an East Asian one based on DNA configuration, not coming from Taiwanese Aborigine or Austronesian DNA.
But overall in every ethnic there must be some East Asian feature as well, this one is Dian Sastrowardoyo from Javanese
Dian Sastrowardoyo (Javanese)
West Sumatran people ( my tribe) who looks like East Asian ( I observe from my big family ) is more similar to a bit Japanese or Korean, and I just know that we call older sister similar like South Korean called their older sister.