It is hard to pin down what is at fault - I have a Pro with a Samsung SSD in an external caddy, and had very occasional stutter during cut-scenes in Yakuza. I'm not having any issues with Resident Evil 7 and load times are massively improved over my SSHD.
I was using Boost Mode with Yakuza though, so it may have been that causing issues. It is hard to be conclusive and it might be wise to wait for a proper tech test from Digital Foundry etc.