To be honest, I think it is actually meant as a nice gesture from U2 to the people of their home country. The Ireland shows always have a huge demand and attract many people from outside Ireland. By publishing the Irish dates later, this makes these people from outside Ireland to secure tickets for other shows, and therefore, these codes will no longer participate in the Irish presale. Which means that the people from Ireland have to compete less with others and have much higher chances to score tickets for the shows in Ireland.
Of course, hope you will eventually score the Irish