I like to believe they were killed like a constrictor kills their prey, by crushing. Due to the inability to swallow, the throat muscles of JJ had to do a lot of work. And just like a python/boa constrictor, the muscles crushed them and rendered them dead
I think that Japan loves tradition, and modern business in Japan also likes jumping into whichever new trend is shown to be working, and those two things usually conflict but this time they've made a tradition of a very specific style of show and it's also currently selling well, so the producers are all going as hard as they can on this trick that kinda satisfies their love of tradition and is also succeeding. Maybe, I don't really know.
Man this scene was so well done. It was absolutely horrific and the fact later in the film we still here them screaming help hours after they were taken up. To think they are in there being disgusted slowly for hours is just absolutely terrifying.
