Aussie John,
You may be aware of other communications https://irelandxo.com/ireland-xo/message-board/letsome-moten-family. Unfortunately, the records in the Census were often written down by the enumerator as many residents were semi- or fully illiterate. This would have led to variations in spelling and ommissions such as the one you've highlighted due to the manner in which the oral answers were perceived and then written down by the enumerator. The same is true for baptismal records as common usage was often written instead of the acutal full name. Hopefully this answers some of your points!