Background
Regarding floats in columns, the wiki states:
By default, a title will be moved down to appear below a float, it will not be "wrapped" around a float like normal text.
Problem
The section title disappears, instead of being moved below the float. Ultimately, I'm trying to produce the following two layouts without changing the content (between \starttext and \stoptext):

As an aside, it is important that the content need not change as there are other layouts that use the same document structure. If content changes can be made universal such that the other layouts remain unaffected, for example by adding a new namespace and command, then that will work. This might resemble:
\definenamespace[Photograph][
type=module,
name=Photograph,
parent=Photograph,
setup=list,
version=1.0,
style=yes,
command=list,
]
% ...
\starttext
\setupInsertPhotograph[
author=Full Name,
homepage=http://authorname.com/about.html,
source=http://flickr.com/authorname/sunset.jpg,
]
% Calls "placefigure" and "externalfigure" using the setup parameters.
\InsertPhotograph
% ...
\stoptext
Then the \InsertPhotograph macro could be used to customize how the photograph is typeset, independently of the layout.
Code
So far, I have the following code:
\setupalign[hz,tolerant,]
\setuphead[chapter][footer=empty,]
\setuphead[section][page=yes,]
\setuphead[subsection][
before={\vskip0.5em},
after={\vskip0.5em},
]
\setuphead[chapter,section,subsection][header=none,number=no,]
\defineitemgroup[Preparation]
\setupitemgroup[Preparation][each][packed][
before={\empty},
]
\setupexternalfigures[width=\hsize,]
\definecolumnset[BookColumns][n=2]
\definecolumnsetspan[BookColumnSpan][n=2]
\starttext
\startchapter[title=Chapter One]
\page
\startcolumnset[BookColumns]
\startsection[title=Section One]
% This could be \InsertPhotograph instead of \placefigure...
\placefigure[tblr]{}{\externalfigure[fake][]}
\startsubsection[title=Subsection]
\input douglas
\stopsubsection
\startsubsection[title=Preparation]
\startPreparation
\dorecurse{4} { \startitem Pour liquid helium into flask. \stopitem }
\stopPreparation
\stopsubsection
\stopsection
\startsection[title=Section Two]
\dorecurse{4} { \input knuth }
\stopsection
\stopcolumnset
\stopchapter
\stoptext
Question
How can the photograph float to the left of the section title when a figure is present, whilst the section title spans the page when no figure is present?

