Usually you have the gun up, but not aimed up (eg at the top few stairs but not above them), otherwise you're blocking your view of threats that are crouched or prone if you have the gun fully up and aimed at a standing adult torso level.

Why wouldn't this be appropriate when clearing a building with unknown threats when dealing with an uncooperative person? The only way it leads to unnecessary injuries is if the officers don't make a proper identification of a threat/non-threat, which can happen with the gun in other positions too.

This type of search wouldn't have been necessary anyways if she had complied immediately. They would have normally asked everyone to exit before doing their search, but once the suspect has been uncooperative and they gain entry they need to be proactive about the search to avoid evidence destruction or suspect fortifications given the suspect's actions. Now had she opened the door quickly, I would agree that the actions would not have been appropriate because you're supposed to clear the building by voluntary means first. In this case, the suspect's family declined that voluntary option by not complying.