No one is going to change the bad habits of new Upwork clients, but why not just put something like "To be determined in agreement with client" in the milestones space and make it clear in your cover letter that your bid is provisional until you get more information, such as seeing the document that needs to be edited and having a phone call to talk through the clients needs and expectations?
Or even include a list of questions you have in your cover letter. My typical cover letter usually includes 8 - 10 questions and no potential client has ever complained that I asked them. (Of course, some clients might have avoided working with me because I asked them questions they couldn't answer. Fair enough, but I don't want to work with a client who is ignorant of or uninterested in the important details of their own project.)
