Perhaps I’m missing something, but my pencil do the double tap into it to swap between clean and last tool used, and I can use the marker to exactly mark over text lines… For this one, if it doesn’t, perhaps your PDF is image-only.
The other is that yes it marks the text, but some PDF app, kind of “line-up” the marking I am making, if I for instance could keep it as a straight line, following the text.