Why are some documents not converted to Google Format?
Sometimes, with Google as the Destination, Google Drive will reject document conversion depending on the document's contents. Some features and characters are not supported by the Google import tool, and thus cannot be converted to Google Docs format.
When a document is not able to be converted to Google format, we migrate it as binary, while still maintaining the correct MIME type. You will be able to open and download the file without problems, though it will not show up as a Google Doc format.