At least for the OCI renewal / re-issue process you don't have to send your US passport along, a copy will do. For a new OCI application, I believe you do have to mail the US passport along with the other documents. That's one thing that would have made me worry, to have my passport sitting in some bureaucratic black hole at VFS for weeks. Not to make you nervous, but just be aware of it, and don't count on traveling internationally while VFS hangs on to your passport. They do return it before the rest of the OCI issue process is completed, though, but it still could be 2-3 weeks as I understand it. In the "good old days" before the pandemic I think there was always an option with CKGS to apply in person, at which point they would have just looked at your passport and given it back to you immediately.