The review you linked to is for the 6 Pro – I’m specifically wondering about the 6S Pro. However, if anyone knows, I would love to know if the 6S Pro and 6 Pro are essentially the same (if the S DOES have an SSD), with the 6 Pro having no SSD, but having an m.2 connector available.
The 6S, 6 Pro and 6S Pro all seem to be the same board and essentially the same tablet. The 6S came with only 4GB of RAM, the 6 Pro with 6GB and the 6S Pro with the SSD drive.
In the video unboxing of the 6S (https://www.youtube.com/watch?v=v8HEirskCng) you get to see inside the tablet and he confirms there is an unpopulated M.2 slot inside which can hold a 2242 or 2260 drive.