I'm not the creator of the Xperia U thread but I'm just telling you
Xperia U ships with 2.3.7
1. The thread maker doesn't know if it's 2.3.7 or 4.0.4 because I have three Xperia U's and they're all running on 2.3.7 and none have gotten the update. You have to flash it manually.
2. The phone has come from abroad where the update has been given to the phone OUT-OF-THE BOX.