The sequential / random access metaphor is interesting, but I believe a better explanation I've seen is that CLI systems require the user to RECALL the proper command -- they can read the manpage to see how to use it, if they can remember what its name is. (Trust me, even after almost 40 years as a Unix programmer, I still have trouble remembering what that command is called that does xxx).
GUI systems, on the other hand, allow the user to RECOGNIZE the proper command -- by looking through menus and applications (or even help remember it for them).
I was just teaching my wife (non-techie) who learned to use the CLI on CP/M and DOS how she can just look at the menus and recognize what to do, instead of trying to recall it.
I've been addicted to the CLI for so long, I ran into a problem where I had trouble communicating with grad students using Linux, because I did everything from the command line, and didn't know how to do some things (like create a symbolic link) from the GUI, and they had no understanding of the command line, except how to type what they were told.
I love OSX because it works well both ways.