Well Bob, the website administrator at my University came up with a fix.
Under Administration and "Scales" make up a custom scale with text entries consisting of every possible mark in your whole series. In my case the scale is called '0_to_20_by_point25' which consists of text entries: 20.00, 19.75, 19.50, 19.25, etc.. He then went into my assignment and changed the scale under the "Grades" setting. (Note that these grades may not be properly interpreted by the gradebook's numeric functions, as the system may see them as text. But if you download the data into Excel it may not matter.)
In my case I don't care if Moodle can add these text labels up or not. It just saves me a big hassle getting marks back to the class (I have 365 all taking the same course.)
Honestly, it's a stupid design flaw, isn't it? You'd think they would provide a patch for this.
Another silly problem that shouldn't exist is that you can't list students by their Surnames when you try to separate them into groups. They only appear by the first names. So in my case I have two sections of students taking the same subject, and I have one website for both. But to separate them into the two classes I have to actually pick through the whole list of almost 400 students by their first names. So I'm just not going to bother. But this again, is a problem that should never even come up. You can sort by Surname elsewhere in the program - why not by groups?