So they aren't charging him with a air choke (much more dangerous), but with a blood choke, which allows air to flow and people to talk, but cuts off blood (and thus oxygen) from the brain.
And the official autopsy found that he was dead
because of the overdose plus police action:
If the pressure on the neck contributed to the death (IANAL, so idk how much it needs to contribute. Maybe it needs to be "absent this, he would have lived", or maybe its "his actions directly contributed to the death." I don't know.), then a conviction for depraved heart murder (he didn't seem to care if Floyd lived or died) is pretty easy, which is 3rd degree murder in Minnesota.
It definitely was a blood choke. Also, why look at the training manual, when you can look at the picture of the actual knee on the actual neck?
We have really good pictures and video of it.
Also, it's possible that the cops were trained to use a blood choke (I haven't seen the training documents), which makes sense, they are usually safe, if not applied for 9 minutes like a crazy person.