Why they hell you keep mentioning knox? Knox is an enterprise solution, via active subscription and onboarding. Knox has nothing to do with FRP or anything. Knox guard devices have to be enrolled using KME/KC or another KG console and have a valid license tied to it.

Fyi - oneui 4.1 also does not do this (tested on s10)

This is just a dick move on their part. In few years to come they will lose more and more customers (I hope so, and I certainly hope I will be fed up by their tactics like these in that time) by removing features like these. When you lose the device these could be the reason you are able to save or at least retrieve something. Or if you forget your pin code, or if your loved one passes away.

I have the base S9 but with 256GB/12GB configuration, I do not need a notebook replacement as I have my mobile workstation for that. I use the tablet for media consumption and time killing.

As for the dofferences, there are a lot of articles online where the tablets differ, its not just screen and processor.