The abstract doesn't really say who was doing the choking or how good they are at it. It's a fairly simple technique to apply. Tighten up around the neck and then "make a muscle" - flex all the muscles in the upper body - reduces the amount of space in the gap through which the person's neck (and, obviously, blood flow) are going.
The hard part is getting getting the choke on, to apply, and in a non-rules environment, not getting your eyes and other body parts gouged, bitten, stabbed, grabbed, etc., while you're trying to sink on a "hadaka jime".
In a rules-environment you can take all the time you want, within limits.
That seems to be the critical issue..... getting the choke on while not getting gouges by fingers (or knives). The issue is first "who is controlling who". If I have my structure, I may even turn the Hadaka Jime into a throw.
I must admit, the police chokes were taught with "safe" methods (only taking blood vessels) for many years and their ideas on stabilizing uke left much room for pivoting of the opponent's body as a defense and counter. The old dogma of "keeping your gunside back" (i.e. blading the body even while you are behind the opponent) skewed proper jujitsu positioning.
I am still convinced that the judo version of chokes is not sufficient. The best choke has the cutter bone of the wrist come up under the coracoid process. It takes air, blood and separates the cervicle vertebrae.
Even using this military version of the choke, one must create kuzushi (position before submission) or the technique can be turned.
I trained both hard and soft neck strengthening techniques. Neck bridges were a good part of that. Just as important were internal forms of exhaling and the consistent stretching of the fascial tissue around the throat as my partner grabbed my gi and pressed his fist laterally against my throat to the laft and then to the right..
I am still convinced that arm bars are superior methods against trained fighters and thus, all fighters. Arm bars are potentially "lethal frce" (just like chokes are). But the choke is lethal by definition. Only the Koppo is lethal in an arm bar. Lethal force being defined as killing or maiming.
When I get home from this tour I am doing, I will attach Hal's 2 on 1 grip basics onto this post. Hal had over 1,000 organized competitive bouths (Judo, AAU Wrestling and Sambo). Few people can make such a claim. He also used his strategy as a cop, as a PI and as a member of Operation 40 (CIA). His strategy on arm bars is genius.