So now the confusion continues... I figured I would go straight to the source - Inspector Ian Yearwood who is in charge of the Traffic & Roads Policing Unit of the RCIPS and got this answer back:
Please note that the visitors permit under the Traffic Law of the Cayman Islands no longer exist.
For countries that do not fall under the Geneva Convention you are permitted to drive in the class vehicle from your country for a period of one (1) month
For countries that do fall under the Geneva Convention you are permitted to drive in the class vehicle from your country for a period of six (6) months.
The Royal Cayman Islands Police has therefore to comply with this law.
So maybe we were ALL wrong!
I have messaged caymanresident.com to get them to independently verify and make changes to their page - I note that the DMV page also hasn't been updated to reflect this. Soon come, I guess.