I think you are confusing classes and components. Your image is displaying the bootstrap classes, which will always be included in the programme. The components, however, are ready made building blocks. If you are running the latest update of RSD, which is called 'SD v. 3', you are in the wrong discussion forum. This one concerns RSD up to v. 2.5, and SD v.3 has its own Site designer forum.
The post of mine that you quoted, is over a year old, from May 2017, when SD v.3 hadn't been launched yet.
As to the building blocks, the components, In RSD v. 2.5 there are quite a number of them. In SD v.3 there are none, I think CC is planning on selling them, and there is a page on this site somewhere announcing them 'coming soon'. Don't know when 'soon' is, though.
Some of us here are trying to assist other users with those building blocks. I have some here: http://horgenhonning.net/sharing/
that you can help yourself to, and others also have some. Just ask what you need, and you may be lucky that someone will help you creating it.
Ha en riktig god dag!
This site was made before we were able to create components through the app:
Component sharing for RFF, RBB, RSD and SD: https://eikweb.com/sharing/
My work in progress right now:
Components for the same as above + HTML Editor: https://mock-up.coffeecup.com