Thanks, oliver2002 for the official bulletin stating that OCIs need not submit the form.

My own experience - landing at BOM a few days ago: FAs still handed out the paper forms on the flight, most people filled those out or grabbed them from the desks in the hallway before immigration. The hallways still have the big signs about filling the form being mandatory, btw. In the immigration hall itself, there were smaller notices, some mounted on the tape barricades that guide you down the lanes to immigration, with a QR code and saying it's faster / more efficient to use the online form. Essentially they don't seem to care currently at BOM whether you use the paper form or the online one.

In my own case, I had the digital file (PDF) from the online submission available on my phone, but the officer processed me without asking for it. After he stamped my passport I asked him if he needed to see the PDF, and he just shook his head, which left me uncertain whether he meant that it wasn't needed because he had all the information from the online submission anyway, or that OCIs did not need to fill it out in the first place. Nothing in the notices at the airport said anything about OCIs being exempt, btw.