Gualbert; a couple of our guys went to check out the MAVO 6K, with their Samsung 860 Pro SSDs, and confirmed that not only is there a discrepancy in size between the KineMAG and Samsung 860 Pro — the KineMAG is thicker — but the 860 Pro actually gets stuck inside the MAVO, and requires a credit card inserted into the SSD slot to remove it. Far from ideal. I believe Kinefinity are being informed about this.
So yes, it sounds like if you want to use third party 7mm SSDs with the MAVO 6K, you will need a spacer for it, like with the KineMAX. Perhaps this is something Kinefinity can / will provide?