In March 2019 Google announced they are deprecating the functionality to obtain a data dump of real-time (RT) Google Drive files:

If you're coming to this article after that date, Google has shut the export down. Generally, this isn't a problem if your file was created or edited after November 2018, or before that but you didn't switch off autosaving of the diagram, which is extremely unlikely.

Either way, there is no action to be taken, this article is just left up for information.