This is true. To preserve document validity and user intent, an algorithm designed for collaborative string editing will not always work correctly when applied to a markup document such as LaTeX, HTML, or Markdown directly.

It is similar to how you need a JSON type to represent the kinds of edits you can do to a JSON document rather than editing JSON text as a string. The kinds of edits done in text better map to editing a markup language like LaTeX or Markdown than JSON, so you are less likely to notice these issues right away. But if the type is designed specifically for the markup language, user intent will be better maintained through concurrent edits and the document will never end up in an invalid format.