Angelfamily, welcome to cruise addicts. As for your question, I have not personally had any bottles taken. I usually pack one bottle of rum. I have no problems. I think the problem is that some people take excessive amount on board.
They use x-ray and they have the right to search your bag. If it is locked they can hold it and have you go to a security location and open it for them, that is usually not done but they do have the right to do it. In most cases they are looking for more than alcohol by x-raying luggage but if they do come across something that looks like a large stash they could very possibly question it, especially Carnival and Royal Caribbean.
They use refurbished last years model airline equipment
The bags lay flat, stand a rum runner up on edge, don't lay it flat in the center. And ya if you have a bottle that looks like a 1.75 ltr of something with a handle on it, you might be put on the booze watch list. Princess and Holland America are usually most lenient, NCL Royal Caribbean, and Carnival are most stringent.
JMO, but it is the luck of the draw if your luggage gets searched. One cruise line searched my luggage and took my shorts and tools-screwdriver and a small pair of pliers(dont ask about the tools). I went to the front desk to question it and they denied that they even search luggage.
6 months later the cruise line returned my tools but no shorts. I did not fill out a report with the cruise line(since they dont search luggage) as at that time I had no proof if it was the cruise line or air line that searched my luggage. No document was enclosed in my luggage and my luggage was locked. oh, no bottle either.