Even if it is allowed that will not, and should not, protect an officer who uses it to kill someone. I don't know of any police force who would recommend killing suspects unnecessarily regardless of method.
The problem with neck pressure is knowing the line. You have to be very observant to what is happening to the individual. When we taught it in the 80s we had an officer in front to observe only and as back-up, even though it lasted only a few seconds..
It will come down to a trainer explaining what training the cop got. If you tase someone and they die of a heart attack you would not usually be charged with murder unless you go overboard on number of shocks. On the neck, the line is not so clearly defined, but to support your point, 5 minutes was way too long. That will be the key question.
Courts have been sympathetic to cops who do what they need to do “in the heat of battle” with a beligerent suspect, but not when they are cuffed and on the ground and three other officers present.
One of the damning things about Rodney King was he had a dozen cops around him and was on his knees.