“if it’s true” to quote your earlier post. You’re wrong to stop questioning it.
Costello is as far from an idiot as they come, so I doubt very much the reason is “We have the jerseys ready, but we’re not going to have them for sale at Christmas in case someone thinks we’re cashing in”.
That means that kids who want a Dublin jersey for Christmas will either get the old one (and be upset when the new one comes out weeks later), or will know only the old one is available so will ask for a soccer or rugby jersey instead.
So I think you’ve been told a whopper. You’d have to be an idiot to implement that decision, and Costello is certainly not an idiot