Just comparing the previous ceremonies announcement with the recent one:
At the ceremony candidates will take an oath of fidelity to the nation and thereby become Irish citizens.
Certificates of naturalisation will issue by registered post at a later date.
November 16th, 2023
At the ceremony candidates will take an oath of fidelity to the nation, receive their certificate of naturalisation and thereby become Irish citizens.
February 9th, 2024
So Hopefully it's not just a mistake. But in the Link provided at the end of the announcement, still not updated (This page was last updated on January 9, 2024) . It still says :
At the ceremony you will take an oath of fidelity to the nation. You do not become an Irish citizen until you have made your declaration. Your certificate of naturalisation will be issued by registered post in the weeks following the ceremony.