Once entering the end, the main island is stretched to abnormal heights and terrain. The obsidian towers do not generate at all, and this appears to make the dragon's behavior extremely faulty. This is the same case in the outer end islands; Some end cities may also be abruptly cut off by the build height limit due to this.

EDIT: I've attached a few images, one showing the extreme terrain, another the total lack of obsidian pillars, and another an end city that was abruptly cut off due to generating too high in this snapshot.