If he leaves, just know the embassy will not make his case a priority to reissue a new visa. There’s a wife in one of my online groups who husband left the country before they approved his travel document. His visa expired so he has to make a new appointment to see a consular officer. The wife has been emailing and calling the embassy and they have yet to schedule her husband an appointment. I guess they feel like he was issued a visa once, so they are not going to push you ahead of others who have not been heard. To answer your question, no he will not have to do the entire process again. The I-131 has a section for those who are outside of the country. You just have to fill that part out and submit it to USCIS. So you can only guess how long that will take 😉