I think that they used Time Machine to add ALL the pictures in your Time Machine files to the existing pictures on your Mac.
Recently because of missing photos in my IPhoto Library local tech folks restored the Library from my Time Machine. At least two problems surfaced as a result of that restoration: 1) Organization of photos in albums was completely lost. No album structure appeared with the restoration. 2) There appears to be massive duplication. The file grew from 36 GB ( some 12,000 photos) to about 60 GB.