Well your above suggestion will not work...
Municipal Corporation of Delhi(MCD) which issued the birth certificate will not change it from Delhi to New Delhi...
Birth Certificate mentions Delhi
Indian Passport mentions New Delhi
Canadian Passport mentioned Delhi
We already had that discussion with Passport Canada when we made the Passport earlier in Sep and they will only go by the Birth Certificate. We did mention that the current Indian passport and CoPR mentions Place of Birth as New Delhi, but they did not budge...
So affidavit is the only way to go.
see towards the end of the page 2 through this link:
https://www.blsindia-canada.com/toronto-jurisdiction/pdf/OCI-Sample-form-with-common-errors.pdf