Hey @kris, thanks for reaching out!
Currently slice variations are not released, they will be somewhen at the beginning of next year hopefully. Preparation work has been made for those that's why you can notice some reference in the model.json file~
So that's why variations are not displayed yet in the content room when you push a slice through the UI too.
I hope this is not a big disappointment for you, I'm also really looking forward to playing with them!
Let me know if anything else 