I am not suggesting Evernote does it without coordinating with draw.io. If you look at their (Draw.io) business model then you can see that Evernote could work with them to enable this feature.
Let's see what Evernote dev thinks of it. I find it useful getting my drawings into evernote and seems like a miss to have to put PNGs/PDFs/XML in manually and keep updating everything whenever the images change.
Thanks for the note, appreciated.