Yes, A filedocument is an object in a table + a file on disk. This this the only entity in Mendix that has this combination. That is why is is always committed to keep it in sync.
The only alternative I can imagine is to store the contents BASE64 encoded in a string (of a seperate entity and thus in database) and do the conversion to a real filedocument later. But that may take server memory.
This can be a complex solution.