I was expecting that video speech is related to structure which is more strict, such as in

Semantic Synchrony:
https://github.com/synchrony/smsn

or editing of database objects.

Of course it is possible to think of "trees", but those trees in text do not really exist unless there is program that is forced to think of tree.

It means there is no "structure". It is only slight viewpoint from a program and programmers to handle some parts of text as "structure".

I would not call text "structured" at all. Of course we can see "structure" from human viewpoint, there is s-exp, there is comment, there is header. We can also "structure" files, this is all true, but in sense of a computer, that is not structured data.

Structured vs. Unstructured Data: What’s the Difference? | IBM:
https://www.ibm.com/cloud/blog/structured-vs-unstructured-data

Structured vs Unstructured Data – What's the Difference?:
https://www.g2.com/articles/structured-vs-unstructured-data