I have a question regarding the shinra company building.

After completing DoC, I went back to watch advent children again. When it comes to the final fight scene between cloud and sephiroth, the whole shinra building was in ruins. One particular scene even shows the top half of the shinra building collapsing.

Now Dirge of Cerberus took place one year after advent children right? Now, if I remember correctly, the whole shinra building is fully intact in DoC! Vincent even went into the building during the last part of the game!

Any reason for this?