InDesign and DPS Classic (2014) would let you assign two separate
inDesign layouts as the sources for the Vertical and Horizontal displays
for the same article. This no longer works in DPS 2015 (2016?)HTML can
be set up as responsive, which means that one HTML layout can "respond"
to how it is being displayed and therefore the design adapts to the
orientation, and one layout serves as the source of both the Vertical
and the Horizontal displays for the one article. This works in both DPS
2015(201...