Visitors who had their evisa validated once (with a rudimentary stamp in the passport) or have a regular visitor visa can use the regular lines. If you have a new evisa which needs to be processed, you go to the long evisa queues. It seems the OCIs are being sent to the latter.

Come to think of it my fingerprints were captured in BOM/DEL/CCU during one of my recent trips (Oct 20 CCU, Mar 21 BOM, Nov 21 DEL or Sep 22 CCU). I'm having a senior moment and can't recall the exact one, but fingers were scanned.