When using the [`libertinus`](https://ctan.org/pkg/libertinus) font and compiling with `xelatex`, selecting the sans italic font with `\textit` causes the bold italic font to be loaded. Why?

```
\documentclass{article}
\usepackage{fontspec}
\setmainfont{Libertinus Sans}

\begin{document}
Test

\textbf{Test}

\textit{Test}
\end{document}

```

[![enter image description here](https://i.stack.imgur.com/leqy3.png)](https://i.stack.imgur.com/leqy3.png)

There is a font called `Libertinus Sans Italic` in the `libertinus` folder, and it seems to be found according to the `.log` file:

```
.................................................
. fontspec info: "defining-font"
. 
. Font family 'LibertinusSans(0)' created for font 'Libertinus Sans' with
. options [Ligatures=TeX].
.  
.  This font family consists of the following NFSS series/shapes:
.  
. - 'normal' (m/n) with NFSS spec.: <->"Libertinus
. Sans/OT:script=latn;language=DFLT;mapping=tex-text;"
. - 'small caps'  (m/sc) with NFSS spec.: <->"Libertinus
. Sans/OT:script=latn;language=DFLT;+smcp;mapping=tex-text;"
. - 'bold' (bx/n) with NFSS spec.: <->"Libertinus
. Sans/B/OT:script=latn;language=DFLT;mapping=tex-text;"
. - 'bold small caps'  (bx/sc) with NFSS spec.: <->"Libertinus
. Sans/B/OT:script=latn;language=DFLT;+smcp;mapping=tex-text;"
. - 'italic' (m/it) with NFSS spec.: <->"Libertinus
. Sans/I/OT:script=latn;language=DFLT;mapping=tex-text;"
. - 'italic small caps'  (m/itsc) with NFSS spec.: <->"Libertinus
. Sans/I/OT:script=latn;language=DFLT;+smcp;mapping=tex-text;"
. - 'bold italic' (bx/it) with NFSS spec.: <->"Libertinus
. Sans/BI/OT:script=latn;language=DFLT;mapping=tex-text;"
. - 'bold italic small caps'  (bx/itsc) with NFSS spec.: <->"Libertinus
. Sans/BI/OT:script=latn;language=DFLT;+smcp;mapping=tex-text;"
.................................................

```