They should just allow you to update the current passport details (and maybe mail in a copy of the new document, duly self attested signed and stamped) online so the OCI card and your passport number are in synch for the immigration system. Similar to how you update your data in the US global entry database. Ironically thats exactly what they have in place to update your current address and profession


They have a point with the faces of children changing at age <20. That is one of the reasons most countries don't issue passports valid for more than 5 years for minors.