Inconsistent letterforms for \mathrm and friends under LuaTeX

[RuixiZhang42]

Description

When using Stylistic Sets to obtain alternative letterforms for text faces, XeTeX will correctly use the changed faces for \mathrm and friends. But LuaTeX will not.

Check/indicate

• [ ] Relevant for XeTeX
• [x] Relevant for LuaTeX
• [x] Issue tracker has been searched for similar issues?

Minimal example demonstrating the issue

\documentclass{article}

\usepackage{amsopn}% For \DeclareMathOperator
\usepackage{fontspec}
\setmainfont{SourceSansPro-Regular.otf}[
  StylisticSet=2
  % Single-story lowercase a and straight-terminal lowercase l
]
\DeclareMathOperator\Stable{Stable}

\begin{document}
\ifx\XeTeXversion\undefined Lua\else Xe\fi LaTeX:
Stable \& $\Stable$.
\end{document}

Further details