Well, probably the way in which that was said has given a false impression, something that happens all the time I am afraid. I will try to clear this up if I can. If you have a small Moodle that uses online self enrollments, then you will not have to worry about it. If you have a Moodle that is accessible only by users of your own network, then at some point before the User accesses Moodle, then they have to become a member of your network. This is the most common option I have worked with, and this is what we do.
Every year we have new enrollments, they have to be registered Users on the network before they can use any of the ICT related resources we have. From there, I ask for a list of new users in the format as a csv file. (The csv file is nothing more than a text file with a set of data that is separated by commas, no spaces, and an extension of *.csv that's all.)
username,idnumber,firstname,lastname,email,
That is all, nothing more. At this point they have not been enrolled in any Moodle Course. We can get as many as four hundred, or as few as 75, depending on the location. I assume the network admin team sets up an automated SQL query that takes data from their database in that specific order. The query runs and I get the data, usually within an hour of me asking for it. I open the file in Excel, but really, any spreadsheet program will do as long as it reads and saves in the csv format. I add the headings,
username,password,firstname,lastname,email
to each column, deleting any existing heading then save it as a csv file again, upload it to Moodle and allow Moodle to work its magic.
That is how the Excel reference comes into it.