Probably not that surprising given that Ireland is a tax haven for most large U.S. corps' presence in all of Europe. If I sign up for AdWords or AdSense now, I'm dealing with Google Ltd, even though I am not in the U.K.
There is no mention of the Republic of Ireland in their earnings report, yet their European headquarters are in Dublin. "U.K." in the report means the U.K. and Ireland.
To include an entire country under the heading of another neighbouring country without making that explicit is a mistake, not an assumption, doubly so when Google have quite large (and distinct) corporate presences in both Ireland and the UK. It wouldn't be too far from Starbucks listing all Canadian and Mexican profits under "United States" when there's a perfectly normal term to describe the geographic region ("North America"), just as there is with the British Isles.