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.
He may have been following his SOPs perfectly. I don't think this is an appropriate SOP for LEOs to use in this situation. I don't think this case called for having weapons drawn at all. My view is that this SOP is likely to contribute to unnecessary civilian injuries and deaths.