I emailed forge world and got this response when askin about the chaos knight and Kytan
"Hi there,
Thanks for the email, with regards to the official rules of the chaos knight and Kytan the experimental rules are for all intense and purpose official, they have been designed and issued by the Forge World studio, the only reason we issue rules with the title of "experimental" is due to it not being published in an imperial armour publication. We are steadily removing this tag from future releases.
The rules for all experimental units should be treated as official until they are removed and published in the related Imperial armour.
Thanks again and I hope this helps"
Hopefully I can start using them at events.