I had almost the complete opposite experience! In one interview, we discussed my ECs very briefly. (perhaps not enough time to really understand them?) And then we spent the majority of the interview discussing philosophy and life and religion and the universe and such. If your ECs are your real passion, then maybe it was a good idea to discuss them. It would have been better for you to ramble about your ECs than to stare at the interviewer awkwardly with nothing to say. At least you let them know that you weren’t just an EC machine!