Hmmmm... I don't really think "give them root level access" is the issue here. I suspect what the issue here is -- and, mind you, this is just a guess -- that the author(s) of the script anticipate needing to make one or more subdirectories within the user's maildir, and on some systems may even need to make the original maildir itself... and, well...
See, if you run the script while logged in as root, or as some other user than the one whos mailbox the mail is intended for, then those newly-created dirs will be owned by root, or that other user, rather than by the intended user of that maildir. which might cause complications when that user later tries to access those mails. At that, the individual mail files might themselves wind up owned by root, instead of by the intended end-user...
It might be possible to chroot the dirs later, I suppose, but...
Anyway, that was one reason I was asking here for input from anyone that has already done this: They might be able to advise me of any pitfalls they ran into, and what they did to work around them. Or they might be able to tell me, "Don't worry about it, everything went perfectly peachy when I did it!"