Got an invite for this today. Never bought anything through the app, and haven't bought anything from one of the partner stores in months either and I don't have an existing HDFC card. The one thing I did was keep the app installed on my phone for a while and show interest in their EMI card in the app. I thought that might get their attention and evidently, it did.
Now a bit conflicted if I should apply for this. I could use the international lounge access for an upcoming trip, but I'm in the middle of waiting to get a preapproved offer for DCP/Regalia. I probably won't, tbh.