Well ... you can't exactly prove your claim so this can be accusationary. :/
Lol i made a video proving this. You can go to the site yourself and checkout the provably fair tab and click on change your client seed. The Next Server seed hash is not shown to you prior to you changing your client seed as their suppose to and have even written they would,
"Technical Implementation
We generate random server and client seeds
You can always change your client seed at the top of this page.
Also we hash server seed using sha256 method.
This value will be shown to you, before you change client seed."
They have yet to implement anything and its been 2 months. I think its fair to say this site is not safe too deposit too.