And they've canonized a movie we all wish wasn't canon!
I think they should have used the one from VI so they looked even older, I think that would have been even more emotional to see that Spock stayed with his friends till he was an old man. It's a minor point though, they didn't look that different, it's not like they used a pic from TOS or TMP, but I can see what they were going for in this scene, so why not use the one where they looked the oldest? Either way it was a brilliant unexpected scene that even my non-trekkie other half found emotional.