This is completely incorrect. The source of the data has been openly announced (several times) as Lufthansa Datasystems, which is the same used for NavDataPro. If one doesn’t like that, Navigraph is usable as well.
Incidentally, MSFS’ database isn’t usable not because they somehow didn’t want to, but because they could not. They’re waiting for Asobo to make it accessible to this kind of custom implementation.