There is the story about a holiday-maker who was lost in Ireland. He stopped and asked the way to Ballymurphy. The person he asked said, "Well. If I was going there, I certainly wouldn't start from here."
The whole point is that you have to start from where you are. And for very many people, starting with the freedom trolley or a home-made trolley is an excellent way in. If you stick with it as some people have done, that simply means that you are happy with it. If you move on to a van-mounted system, that simply means that the system suits you better.
Neither one is superior to the other in every case.
We are all different individuals and different things suit us at different times and at different stages of our development.
There is a principle called Ashby's Law of Requisite Variety which states that the part of the system which has the greatest flexibility of response, exerts the greatest control. Think about that at the appropriate speed and play with the ideas in a variety of ways and learnings will occur.