Jobe starts Octave with a command of the form
octave --version --norc --no-window-system --silent -H prog.m
The --norc will prevent autoloading of packages. I don't remember all the details, but I don't think you can remove that option as the task is running as user Jobe, who for security reasons has no home directory.
I installed the statistics package on my development server and was able to submit an Octave answer that began
pkg load statistics
So can you not just clone the octave_function question prototype (or whatever prototype you're using) and edit it so it begins
pkg load statistics {{ STUDENT_ANSWER }}
?
You could call your new question type octave_stats or some such.
That has the slight disadvantage that error line numbers seen by the students will be out by one but students soon learn not to trust error line numbers anyway.