The transparent header template is designed to be used with a block that has a background image or a solid color (e.g. a cover block), so that the image or color will show through behind the transparent header.
Because of this, it does not display the post title because otherwise the post title would be displayed behind the logo/menu header.
You can write the post title as the text/heading in the cover block or as a separate heading block.
When you add a heading block it will be a H2 heading by default but you can change it to a H1 heading, and also standard paragraph text can be changed to a H1 heading if you prefer.