Hi! This is another unintuitive behavior I have to say. The text style was offered when you created the text. But, once the text is created, it cannot be easily changed within the text editor. You can change it in a different dropdown menu however. Select the text object (without editing it) -> Annotate -> go to far right -> find the style dropdown. Click it and you will see the available text styles to choose.
The main reason for this behavior is that most objects, if not all in the drawing are driven by styles and standards. It is good to enforce rules within a company. As a result, most of the drawing workflows were designed to enforce the styles and standards.
Many thanks!
Johnson Shiue (johnson.shiue@autodesk.com)
Software Test Engineer