This concerns ePubs exported from ID CS 6. The idea of reflowable text is that if you change the window size, the text will reflow to fill in the new dimensions of the window. But I notice this is not true with the toc. Looking at the ePub in Adobe Digital Editions, if I drag the right side of the window to the left, the text reflows, but the list in the toc just gets covered up. Shouldn't the toc reflow also?
ADE is buggy. That's one of the bugs. But most people will probably not
be using ADE to read your ePub anyway.
Having said that, the reflowable part of an ePub refers to the actual
text (in the right hand pane in ADE), not to the navigation pane.
Different ePubs readers use different ways of displaying the navigation