I agree on both points; it was a plea to show “he’s black enough”. And it would be a significant problem if he used another passport. However, my understanding of Indonesian law is that - if you are an adopted child, you have to claim the Indonesian citizenship at the age of 18 (there’s like a 6 month window) or you lose it. Much like with Canada and other nations.
If he didn’t claim it, then no passport, no problem. If he did claim it, then he automatically forsook his US citizenship.
Personally, I think the BC issue is a red herring put out to drive conspiracy theories. It’s done quite well at that! What’s a few million dollars to distract a portion of your political opponents, especially in a day and age where you’ll spend $400+ million on a campaign?
Indonesian citizenship is exclusive. If his stepfather took out citizenship papers for him, he had to renaturalize on reentering the U.S. Did he do that? Did his mother do that for him? Remember, she was supposedly an Indonesian citizen herself when she died.