At risk of sounding critical of the Irish, the BMD records are not 100% correct for this period. My own grandfather was born in about 1880 in Galway but his birth does not seem to have been registered at the time though he was baptised. Several of his siblings were baptised before birth (if you believe the paper records) too!!
Well, with many being patriotic, you don't think they were going to support the British administration, do you? And at a cost to themselves!
As regards premature baptisms, so called, that is relatively easy to understand given the circumstances of the day. My grandmother and her sisters were all born in the 19th century. Over 50 years ago I enquired why we never celebrated her birthday. She explained that birthdays were never celebrated in her generation, and many didn't know what their birthday was. Further, her parents and grandparents generation did not live by the calendar, and would not have been able to read a calendar in any case. As a specific example, my grandmother was well educated with a boarding school education, but her father was illiterate, as was her grandparents.
Putting this all together, if there is a discrepancy as to the date, I always go with the earlier one.