dvi output contains no info about variable fonts

[anntzer]

The following two documents differ by the application of a custom weight on an OpenType variable font (which can be downloaded from https://github.com/googlefonts/roboto-flex):

\documentclass{article}
\usepackage{fontspec}
\begin{document}
\thispagestyle{empty}
\fontspec{Roboto Flex.ttf}foo
\end{document}

\documentclass{article}
\usepackage{fontspec}
\begin{document}
\thispagestyle{empty}
\fontspec{Roboto Flex.ttf}[Weight=700]foo
\end{document}

Indeed, compiling to pdf with luahbtex 1.21.0 (texlive 2025) correctly shows the weight difference. Yet, compiling with --output-format=dvi results in two identical dvi files AFAICT (except for the timestamp).
It would be appreciated (for the purpose of developing dvi viewers) if the variation axis info was kept in the dvi file.