That sounded to me like a reference to using the REPL + GUI in an interactive session vs. writing a code file that is saved.

Some (many?) use MATLAB interactively to produce figures and then save them by hand. Often this involves a mixture of typing commands and clicking on GUI elements like "add colorbar". So a m-file that produces the figure doesn't exist; at best there would be fragments of code buried in MATLAB's command history.