The "hour-long series of turns" themselves suggest that it was not a hijacking - one would expect a hijacked airplane to head towards its intended destination, regardless of the motive for the hijacking.
It does not seem likely that the path was intended to avoid detection, as it crosses Malaysia and was within range of Indonesian radar throughout that period, and it is rather implausible to suggest that these posited hijackers both wanted to be stealthy, yet chose a route that had no chance of achieving it. If these posited hijackers wanted their arrival at their intended destination to be a surprise, their best hope of achieving it would be to stage a hijacking on a flight close to that destination.
I guess one could suppose that this is the only flight the posited hijackers could hijack (suggesting help from insiders at the airline), and that the flight was intended to stay away from land as far as possible, but where, especially with that final turn, were they going? If their destination was, as has been suggested, Kazakhstan, they could hardly hope to avoid detection later in the flight. Nor would they be likely to suspect that the reporting of the disappearance of the flight would be delayed by hours.
The author did not say that this track proves it was not a hijacking, he wrote that it already "suggested that this was not a standard case of a hijacking."