material swapped with \subsection in AMS document classes

Question

I today saw very interesting case when subsection started by shaded environment

\documentclass{amsbook}%{amsart}
\usepackage{xcolor}
\usepackage{framed}
\newtheorem{theorem}{Theorem}[section]
\newenvironment{Shaded}{%
\def\FrameCommand{\fboxsep1pt \colorbox{shadecolor}}%
  \MakeFramed {\FrameRestore}}%
 {\endMakeFramed}
\newenvironment{ShadedTheorem}
{
\definecolor{shadecolor}{rgb}{.94,.96,.94}%
\begin{Shaded}%
\begin{theorem}%
}{%
\end{theorem}%
\end{Shaded}%
}
\begin{document}
\subsection{Bad Subsection}
\begin{ShadedTheorem}
        Bad Theorem: is moved
\end{ShadedTheorem}
\subsection{Okay without shading}
\begin{theorem}
        Good theorem
\end{theorem}
\subsection{Subsection with text first}
Okay if shaded theorem is not the first object
\begin{ShadedTheorem}
        Theorem Statement
\end{ShadedTheorem}
\subsection{Subsection with space first OK}~
\begin{ShadedTheorem}
        Theorem Statement
\end{ShadedTheorem}
\subsection{Subsection with \texttt{\textbackslash par} first: not okay}\par
\begin{ShadedTheorem}
        Theorem Statement
\end{ShadedTheorem}
\subsection{Subsection, leave vertical mode first, then enter vertical mode again.}\leavevmode\par
\begin{ShadedTheorem}
        Theorem Statement
\end{ShadedTheorem}
\end{document}

In all cases the shaded theorem should appear after the section heading. But that's not what the output shows.

In general as you can see there is way around. However somebody may see similar case and need some solution. Also may be there are solution different from what I found