The idea that the airplane was flown to higher altitude to disable the passengers is beyond silliness. It would demonstrate the perpetrator is not really all that smart or aware of the available options
And i am still confused, did all this supposedly occur ( changes in altitude) before or after the transponder stopped working. If after, how do they know the altitudes? If the data is coming from another source Like flight tracker, then that opens a whole new series of questions.
If it occurred before the transponder stopped working, then there are many other plausible options aside from a land shark coming up and biting them
The article describes the sequence of events.