Currently you can import charges based on student name + user ID.
You should be able to import charges based on user ID alone. There is a large opportunity for errors with names i.e. misspelling, nicknames, students with the same name etc. In SB7 you could import with just a user or student ID only.
I'll just say that I've actually appreciated the multiple field verification on other imports (like decisions) because it serves as an additional check to ensure data integrity. For example, someone accidentally dragged a user id cell and switched it with the cell underneath, which would have possibly resulted in a user getting the wrong decision. Anyways, that's just been my experience.