It's just not this automatic outcome.

I actually think that most people (especially a young teenage girl) would probably not be able to exert enough force or strike at the appropriate angles and body locations to kill somebody with a knife.

Certainly not with one blow. Which is about all Ma'Khia would have had the seconds to attempt if the police had been serious about de-escalating/restraining her instead of exterminating her.

Thae one stat I quoted up top, which I think was from UK data, estimates that 85% of stab wounds don't even go beyond subcutaneous tissue. Most knives in people's homes probably aren't even maintained/sharpened properly enough to be an effective murder weapon.

Even Julius Caeser needed to be stabbed repeatedly by multiple grown ass men circled around him to be killed on the spot by stabbing lol