Interesting and confusing.
The histfam and Ancestry sites describe things a little differently. Here are the records for the same person:
Born in Plas Y Glyn, Anglesey, Wales on 11 Feb 1789 to Edward Elias and Elizabeth Parry (Ancestry.com)
Plas-y-Glyn, Clynnog, Caernarvonshire, Wales (histfam)
I would tend towards the former which is sourced to the pedigrees of caernarvonshire which as I understand it was very much based on source records.