I thought about this possibility, too.
Also note that you can manually add listening time. As you can see for French, I have listening time similar to the people mentioned here, because when I listen to a podcast or French radio I just add 30 minutes or an hour manually. In fact my actual hours are significantly higher because I tend to forget.
I don’t think there’s any limit on what you can enter; if you want to enter 30 hours because you never knew the feature existed, and want to add a guess for all the listening you’ve done already, I think there’s nothing stopping you. If you want to add 1000 hours to be the ultimate king of language learning, I guess you could do that too (but what’s the point?).