In other places, it appears directly in small areas with clear sky below.
Later, Malaysian authorities tried to replicate this event with a reconstruction excercise and were unsuccessful.
Right now everything feels like new evidence, so the theory I wrote feels like the most plausible explanation.
Spoiler with annotations for identified features.
The captain could not possibly have known in advance that a Chinese agent was going to be on board MH370, therefore your question about the inclusion of Diego Garcia in the standard Microsoft Flight Simulator product is irrelevant in this context.
Retrieved 28 September 2014.