`CharacterVariant` doesn't work for smaller font sizes with LuaTeX

[teatimeguest]

Description

When using LuaTeX, the CharacterVariant feature doesn't work for small font sizes such as \scriptstyle and \footnotesize. This problem doesn't occur with XeTeX.

• ✗ Relevant for XeTeX
• ✓ Relevant for LuaTeX
• ✓ Issue tracker has been searched for similar issues?

Minimal example demonstrating the issue

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{STIXTwoMath-Regular.otf}[CharacterVariant=3]
\begin{document}
  $\varnothing$
  % The following produce incorrect output:
  $\scriptstyle\varnothing$
  $\scriptscriptstyle\varnothing$
  \footnotesize$\varnothing$
  \scriptsize$\varnothing$
  \tiny$\varnothing$
\end{document}

Further details

Compiling the above code yields the following output:

• with LuaTeX

  

• with XeTeX