Why are some of the tutorials and documents grayed out?

I was looking at the articles indocs.unrealengine.com page and saw some tutorials such as destructibility are semi-transparent. Why? Thanks, waiting for a response.

Hi JHanziwest,

Many of these tutorials were pulled so that we could update their content or polish them to make sure the tutorials/documents reach Epic standards. These may be released in the future, however in their current state they are not ready. Thank you and have a great day!