This still wouldnt be enough, because you could still target the unique mix of script/script versions some specific site has, and have a high chance of being accurate, or at least high enough for statistical purposes.
If the site doesn't want to leak that information, it doesn't participate in cache sharing. Since sharing is opt-in, sites won't unknowingly leak this information.
Edit: whoops. I see what you mean. I missed an edit while modifying an earlier draft and left the opt-in only on one side, the sharer.