Well, I'm not sure that I can further explain it, or explain it any better, because, now, I can't get it to work either.
:-\
What I know is that, I'd get these recurring notifications to update to Safari 6.0.2 via the App Store, and I won't do that until I can find a downloadable file to distribute across my Macs.
Anyway - I got tired of seeing the update notice, so I clicked on the "More" link (because I had 2 updates pending), and when they 'itemized' themselves (2 separate listings), I was able to Right-Click on the names of each, and choose "Hide Update."
Now, I've got 2 updates pending for a couple of stupid games that I downloaded to my iPad, and it won't let me hide them! I don't get it.
Has Apple completely dumped the concept of consistency?
Wait a minute! I just realized something: I'm currently working on my older Mac Pro (1,1) which doesn't support Mountain Lion, so I'm running OS X 10.7.5 just as you are - and THAT's why neither of us can see the "Hide Update" when we Right Click…
I am able to do this on my newer 12-Core under Mountain Lion.
Sorry that I wasted your time.