Unclear! Different news articles are saying different things and meanwhile there is nothing official on this matter on the government web sites.
I sent an e-mail asking about this to the contact address listed on the E-visa web site, but no response yet.

I'm flying to India shortly. I'm going to fill the online form in anyway, it's unlikely they'd object to someone filling it in if they don't have to (OCI), and it's better than facing any undue delays at immigration because I didn't fill it out when I was supposed to.
As always, the rule of thumb with paperwork in India is, "the more the merrier".