According to this post, the top bar's height has been changed to 50px on all Stack Exchange sites in order to have the same height on Stack Overflow and on other sites. However, on Super User, the top bar's height is still 40px. I've looked at Stack Overflow, Meta Stack Exchange and a few other random sites, and their top bars are all 50px high. According to what I've seen, it's only Super User that has a 40px high top bar.
Also, the search box is lighter on Super User than on other sites. On Meta Stack Exchange and other sites, the search box was made darker as a result of this post, but it hasn't changed on Super User.
So it seems like Super User still has the same top bar as there was on other sites when the new top bar was first implemented. Is there any reason for this?