Isn't ListLookup function now in O365? How to query a SharePoint list from another list in Nintex Forms for O365. This Doc could now mention that. The new method is Lookup Runtime in Nintex Forms for Office 365. I think the older document could be marked outdata, but it is still really good information and the technique could be used for many other applications to different scenarios. But the July 2016 release made it outdated.
There are a lot of questions to this document left unanswered that the product team will want to review.People Picker Extensions - Nintex Forms Questions on use in O365. Also, there are some typos in the original code in the top section of the document.