<$rst_scene> works for ebook but not manuscript exports

When exporting to epub, I edited Chapter Heading in Compile Format Designer and in Title Options I set Title Prefix to

Chapter <$n>

which renders as something like

Chapter 1
The Name Of The Chapter

correctly in the epub.

However when I make the corresponding change to Chapter Heading for (a copy of) “Manuscript (Courier)”, the <$rst_scene> is just blank.

The name of the chapter is included (or not) depending on whether the Title option is checked for the Section Layout you’re using. The <$rst_scene> placeholder resets scene numbers; it has nothing to do with the chapter title.

The preview text in the Section Layout editor should show you whether the title is included or not.