[cynwoody]

Using the passport is a significant act re citizenship.

The State Department doesn't seem to think so.

If it were to come out that he'd formally renounced his US citizenship as an adult in front of an Indonesian consular official in order to get the thing renewed, that would be a problem.

[expatpat]

That is not relevant to this situation, because it relates to dual citizenship. The situation with Indonesia is different because Indonesia does not accept dual citizenship - you are either an Indonesian or you are not. If not you cannot have an Indonesian passport.