It's fun to work with non-linear notebooks both as it's creator and reader.
As a creator, you don't have to silo your notes into one bucket (subject) like you had to in school. Complex ideas arise from simpler ideas from different disciplines, so it makes sense for a passage about say, the direction of modern science, to have backlinks to something about the history of capitalism, imperialism, and national defense - all of which can be explored in themselves.
When the graph of these ideas are complex enough, the digital garden will be like a choose-your-own-adventure game in the context of someone's mind. To traverse a digital garden is to interactively follow someone's line of thinking. You can pinpoint where logic might be broken, and maybe point it out. Because each idea is still in its early stage, it's unlikely that you'll agree with all of them. This is to the point of digital gardens since the purpose is to capture and cultivate early-stage ideas and build on them given new information and feedback