As a follow-up; I had contacted Pioneer about my password issue and was waiting on a reply when I came across this thread. I thought I'd try the script instead of waiting for a reply, which worked perfectly for me.
Turns out the Pioneer tech support team is extremely helpful. They sent through these instructions for me to clear my password. I haven't personally tried it as I had already run the script in this thread. If the script isn't working for anyone and you'd like to try an official alternative method to reset the password (not remove the prompt completely as this script does) please see the attached picture with instructions.
I'm not sure which models this will work for as the reply to my email was specific to my AVIC F840BT. I'm sure other models with a similar password prompt will likely have the same procedure.
I didn't think posting this would be more of an issue for theft than this script already is. Either method is easy and does the same thing so...