I think I get it now. The different type of sections – pages, files, fields, info – have to be kept apart in separate sections.
title: Site
sections:
listed: # this is a section within the 'sections' this can be called anything perhaps section_a
type: pages
status: listed
image: icon
content: # # this is a section within the 'sections' this can be called anything perhaps section_b
type: fields
fields:
So the ‘sections’ is divided into two sections, one for the pages section and one for the fields section.
And it seems that even if there is only one section the Blueprint still needs to have:
sections:
section_a: