Probably just a clever ad campaign. If you live in the UK, you would probably buy one to see if it tastes different.
I just spent a full minute with an enticing 3X scale image of a split open Cadbury egg in front of me, increasing the chance that I might grab a pack the next time I am in the grocery store!
Since the product is appearing in stores now, they had to make the decision months ago. But now is the time for press release. If they were really worried about bad publicity, they would have announced earlier so people would have somewhat forgotten by now.
Probably cost Cadbury about $100 to put out the announcement. Pretty sweet investment!