Doesn’t sound like this pilot theory was the case - the plane was experiencing unexpected drops in altitude amid severe thunderstorms, the (controlled) 6000ft drop didn’t happen until afterwards and was a completely standard autopilot manoeuvre.
1 person died and dozens were injured when Singapore Airlines flight SQ321 experienced turbulence near Thailand.
www.flightradar24.com
The information being released is pretty amateur, so I am just coming up with realistic theories based on the data and also what people have said (which is interesting as most people are clueless about flying, even the ones on the plane it happened with, so it isn't really reliable). That said, a few things don't match up. Going by one passenger's own account, people got hurt and were doing cartwheels during the '6000 ft drop' (which was part of the actual descent) this was after the so called severe turbulence. Looking at the data, the pilot-instructed descent happened 14 minutes after this period of severe turbulence (where the flight bounced around quite badly for a minute or two - and it did according to FR24 data). Another passenger has also said that this wasn't too bad however.
Singapore Airlines will know exactly what has happened, but the fact they aren't saying anything useful whilst the media are getting things wrong or giving the microphone to unqualified people is a bit suspicious at worst, frustrating at best. There's potentially some criticism coming the way of the airline or flight crew, and given that they have a fatality, are probably being appropriately quiet.
Another factor is that the altitude and vertical speed (which was pretty typical for a B777) may not paint such a full picture over a shorter period of time, especially in an area where ADS-B coverage isn't great (this is what Fight Radar 24 uses). Spikes happen regularly, for example, and their blog is always full of people posting stuff about planes dropping out of the sky, when in actual fact there was a lag or poor data for moments here or there.
I still suspect something is off about this. 'One dies during turbulence' doesn't sit right with me, especially as it seems like he had a heart attack. Either the diversion was attempted due to medical emergency aggressively without much warning to the passengers (which caused the wreck to the cabin and the actual turbulence is a bit of a red herring), or simply the turbulence was actually bad, but the weather should have been clear, but not acted upon and avoided. I'll be watching it unfold with interest!