That's one interpretation. The technique the officer used is in fact the one approved by the department.
Have you seen the video?
RAW: George Floyd body cam footage
There is nothing in their policy that says they need to continue doing it for 9 minutes after the suspect is controlled and placed in custody. In fact, their policy is for them to stop once the suspect is under control. The aim is to not have folks die in police custody, and certainly not to be kneeling on their neck when it happens... Had this been the case this craptastic narcissist would have noticed him having issues breathing and called an ambulance. Instead, he had to show everybody around there that he was "the boss" and that "they couldn't tell him what to do" and ignored the distressed health of a man in custody.
Now, as for your claim that the ME said that his death wasn't homicide only means you didn't read the actual autopsy report where the ME noted: The Hennepin County medical examiner found fentanyl in Floyd’s system, but the autopsy said the cause of his death was “cardiopulmonary arrest complicating law-enforcement subdual restraint, and neck compression.”
The ME also ruled the death to be a homicide.
https://www.newsweek.com/george-floyd-autopsy-report-cause-death-1579393