It's a lot more complicated than them "keeping him waiting". The consular process (interview in Indonesia) will result in his getting an immigrant visa. He will become a Green card holder immediately when he enters the US with that visa. Adjustment of Status, on the other hand, will require him to submit an I-485, an I-131, and an I-765. He will then have to wait months and months to receive a Green card. Unless otherwise authorized, he will not be able to work until he receives an approved Employment Authorization Document. That could take as long as 8 months. In addition, he will not be able to leave the US without approved advance parole.
As you can see, there is a huge difference between consular processing interview and adjustment of status. He should discuss all this with his attorney.