[pretest]: xelatex selects semibold instead of bold

[Uwe Siart]

When I run the following MWE through xelatex it selects Libertinus Serif
Semibold instead of Libertinus Serif Bold unless I set explicitely
[BoldFont = * Bold].

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Libertinus Serif}
\setsansfont{Libertinus Sans}
\begin{document}
Regular text and \textbf{boldface text}
\end{document}

I don't know if this is intended behaviour and when it was introduced.
But I think (but I'm not 100% sure) it was different in TL18.

Also, if this is an issue at all, I don't know whether it needs to be
fixed upstream or whether it is an issue with TL config files. So
please excuse if this is the wrong place to report.

-- 
Uwe