Isn’t this a little like saying that because I can’t express myself well in Finnish, I probably can’t express myself well in English? Or maybe more like saying that writing about a topic and speaking about it are completely linked?

There’s a difference between having/understanding an idea and being able to express it in different modes/mediums of communication (in this case, to computers vs to humans). I’m not saying that one can’t learn to be better at a form of communication, but I recognize they are different abilities.