siunitx：警告“\textsuperscript 在数学模式下无效”且缺少空格

Question

这些警告/错误有合理的解释吗？

我该如何正确避免它们？

如果我使用 pdfLaTeX，我会得到相同（不正确）的输出，但没有警告。

%!TEX TS-program = lualatex
\documentclass[fleqn]{scrartcl}

\usepackage{fontspec, polyglossia}
\setdefaultlanguage[spelling=new, babelshorthands=true]{german}

\usepackage{mathtools}    
\usepackage{siunitx}

\begin{document}


%Warning: LaTeX Warning: Command \textsuperscript invalid in math mode on input line XYZ
%The non-marked lines are ok


\[ \SI{1}{\cm^3 \per \min} \]
\[ \SI{1}{\cubic \cm \per \min} \] %warning
\[ \SI{1}{\square\cm\per\min} \] %warning
%\[ \SI{1}{cm^2 \per.       min} \]
\[ \SI{1}{\cm^2 \per \min} \]
\[ \SI{1}{\N \cm\tothe{3} \kilo \mol\squared}\]
\[ \SI{1}{\N \cm\tothe{3} \min} \] %warning and visibly missing space between N cm
\[ \SI{1}{\cm\tothe{3} \min} \] %warning
\[ \SI{1}{\cm\cubed \per \min} \] %warning
\[\SI{1}{\N \cm \tothe{3} \kilo \gram \squared}\] 

\[\SI{1}{\N \cm \tothe{3} \kilo \gram \squared}\] 
\[\SI{1}{\N \cm \tothe{3} \kilo \mol \squared}\]

\end{document}