It doesn't necessitate pure tree structure. The visuals are like conventional programming languages even if the underlying structure is tree-like. (Which is essentially the case anyway for any AST-based language.) Comments and other metadata are annotated onto the AST. (For example, English identifiers. In this way, a module of code can have an overlay of names in English, a French overlay, etc. And renaming a function or variable doesn't cause a rebuild or break any references because nothing is referenced by human-language names internally, even though it appears as so in the editor.)

Yes, the idea is to unify the structure editor with version control. Having the entire history of how nodes were moved around in the code gives you perfect knowledge of what was moved where or changed into something else, unlike line-based editing, where the problem is AI-complete.