siunitx 'detect-all' does not honor fontspec's math font in Beamer

Question

Problem statement

The \sisetup{detect-all} option of the siunitx package does not work for me as expected in a Beamer presentation, which I would like to typeset as follows:

• Text in Latin Modern Sans (sans serif)
• Math in TeX Gyre Pagella Math (serif)

For reasons beyond this MWE, my setup requires lualatex and \usepackage{siunitx}. I would like the siunitx package to detect whether it is being used in text or math mode and adjust the font accordingly, which I understand is typically done using \sisetup{detect-all}.

MWE to illustrate the problem

The following MWE (compiled with lualatex) shows how Beamer incorrectly uses the sans font for siunitx macros in math mode.

\documentclass{beamer}

\usefonttheme{professionalfonts}% Turn fonts over to 'fontspec'
%\usefonttheme[onlymath]{serif}% Does /not/ solve the problem

\usepackage{fontspec}%
\setmainfont{TeX Gyre Schola}%
\setsansfont{Latin Modern Sans}%

\usepackage{unicode-math}%
\setmathfont{TeX Gyre Pagella Math}%

\usepackage{siunitx}%

\sisetup{%
  detect-all,%
}%


\begin{document}

\begin{frame}
  \begin{itemize}
    \item Regular numbers in text mode: sans font, as expected: 2469
    \item SI numbers in text mode: sans font, as expected: \num{2469}
    \item Numbers in math mode: math font, as expected: $2469$
    \item SI numbers in math mode: sans font (not expected): $\num{2469}$  % <== !!!
  \end{itemize}
\end{frame}

\end{document}

MWE to demonstrate that this problem is specific to Beamer

It appears that this problem is specific to \documentclass{beamer}, since the following MWE for \documentclass{article} (again compiled with lualatex) works entirely as expected.

\documentclass{article}%

\usepackage{fontspec}%
\setmainfont{TeX Gyre Schola}%
\setsansfont{Latin Modern Sans}%

\usepackage{unicode-math}%
\setmathfont{TeX Gyre Pagella Math}%

\usepackage{siunitx}%

\sisetup{%
  detect-all,%
}%

\begin{document}

  \begin{itemize}
    \item Regular numbers in text mode: main font, as expected: 2469
    \item SI numbers in text mode: main font, as expected: \num{2469}
    \item Numbers in math mode: math font, as expected: $2469$
    \item SI numbers in math mode: math font, as expected: $\num{2469}$
  \end{itemize}

\end{document}

Non-satisfactory workaround

In the following MWE, which was inspired by this post and compiled with lualatex, siunitx commands use the correct math font. I've added an additional equation* environment to distinguish between inline and display math (as the required \sisetup options that I have added also do).

\documentclass{beamer}

\usefonttheme{professionalfonts}% Turn fonts over to 'fontspec'
%\usefonttheme[onlymath]{serif}% Did /not/ solve the problem

\usepackage{fontspec}%
\setmainfont{TeX Gyre Schola}%
\setsansfont{Latin Modern Sans}%

\usepackage{unicode-math}%
\setmathfont{TeX Gyre Pagella Math}%
\newfontfamily\mymathfont{TeX Gyre Pagella Math}% <== NEWLY ADDED

\usepackage{siunitx}

\sisetup{%
  math-rm=\mymathfont,%       <== NEWLY ADDED
  detect-all,%
  detect-display-math=true,%  <== NEWLY ADDED
  detect-inline-family=math,% <== NEWLY ADDED
  detect-inline-weight=math,% <== NEWLY ADDED
}%


\begin{document}

\begin{frame}
  \begin{itemize}
    \item Regular numbers in text mode: sans font, as expected: 2469
    \item SI numbers in text mode: sans font, as expected: \num{2469}
          \item Numbers in math mode: math font, as expected: $2469$
    \item SI numbers in inline math: math font (now as expected): $\num{2469}$% <== NOW WORKS
    \item SI numbers in display math: math font (as expected)
      \begin{equation*}
        \num{2469}
      \end{equation*}
  \end{itemize}
\end{frame}

\end{document}

Why I do not consider this workaround a satisfactory solution

• In an example more complex than the above MWEs, the workaround breaks compilation (I'm still analyzing why that might be the case)
• I still do not know why the problem only appears in Beamer, but not article, which makes me think that a more satisfactory solution might actually have to be grounded in Beamer, not siunitx.
• I now need to effectively define my math font twice, which makes the code harder to maintain.

Answer 1

This works for roughly the reasons explained in the comments:

\documentclass{beamer}
\usefonttheme{professionalfonts}
\usefonttheme{serif}
\usepackage{fontspec}
\setmainfont{Latin Modern Sans}%TeX Gyre Schola}
% \setsansfont{Latin Modern Sans}
\usepackage{unicode-math}
\setmathfont{TeX Gyre Pagella Math}
\usepackage{siunitx}
\sisetup{%
  detect-all,%
}
\begin{document}
\begin{frame}
  \begin{itemize}
    \item Regular numbers in text mode: sans font, as expected: 24693
    \item SI numbers in text mode: sans font, as expected: \num{24693}
    \item Numbers in math mode: math font, as expected: $24693$
    \item SI numbers in math mode: sans font (not expected): $\num{24693}$  % <== !!!
  \end{itemize}
  \[ \sin \theta^2 + \cos \theta^2 = 1 \num{2469} \]
  $x^3 + f(y) = \sqrt[5]{z}$

  1234567890

  $1234567890$

  $\num{1234567890}$
\end{frame}
\end{document}