Also, Lewis, one of the developers at A2A Simulations has said the following three days ago about MSFS 2020 SDK in response to the SDK issues Aeroplane Heaven devs are having:
Unlike the past versions of MSFS the SDK is not being used by the platform studio to make the aircraft but rather the SDK is being built after the fact. Which any software developer will tell you is always asking for trouble and is arguably the wrong way to go about it. A working example; When game developers advertise a mission editor or model importer in a game as something they used the make the game, you see how this is the ‘correct way’ to do such things and why its so often advertised as a marketing feature of a given Game.
Source: Redirecting... and Aeroplane Heaven