This is completely wrong.
First of all the word "expat" does not exist in legal terms. An individual can be a citizen, resident, non-resident, non-domiciled, immigrant .... .
Second, ever studied the term "habitual abode" or Portugal tax legislation or Philippine tax legislation or Egyptian tax legislation?
Before claiming that more than 200 countries on Planet Earth obey to your made-up generalization of "six months"
please do all of us favor and go over the books again.
Furthermore, learn about the matter: This is about residency and the person intending to reside in Indonesia. That makes him automatically a tax resident in Indonesia. Study the applicable legislation!
Third, never say he/she is "misguiding people". Choose your words more wisely!