Back in the beginning (like when I released v3 or so, by the time I got it on MG) they used to monitor when I made version number changes on my webpage and then updated MG copy of d7 accordingly. Somewhere along the line I stopped putting the version number on d7's homepage and MG stopped updating it. I don't know which happened first. They could use the webpage for the release notes to keep up with things, but they actually still do a lot of their news/updating manually, so I didn't press the issue at all. With all the apps on MG I'd hate to be one to complain that they didn't manually update d7's listing EVERY SINGLE TIME I updated d7, which we all know would keep them working their butts off to keep up with me haha.
Long story short, every time I have a significant free version release (IF I remember to) I will email Tim to update their mirror. I just need to remember to do this more frequently. I did it with v10 and v10.0.5 recently, but before that... well I didn't notice until a week or two ago I had a new d7 user in a situation point out to me that MG was still pushing v7. Yikes.