Cyrillic glyphs in Serif Semibold Italic are not so very italic

[alerque]

I'm not sure what the history is for Cryrillic Semibold Italics, but honestly they look more like slanted Romans than italics to me!

Here is some test code and sample thanks to @d125q, extracted from this comment:

LuaLaTeX code

\documentclass[preview]{standalone}

\RequirePackage{xpatch}
\RequirePackage{xcolor}
\RequirePackage[american]{babel}
\RequirePackage{enumitem}

\setlist[description]{%
  leftmargin=*,%
  font=\mdseries\ttfamily,%
}

\babelprovide[import]{macedonian}
\babelprovide[import]{serbian}
\babelprovide[import]{russian}

\NewDocumentCommand{\FontName}{}{Libertinus}
\NewDocumentCommand{\LoadFont}{mo}{%
  \babelfont[#1]{rm}[%
  Language=\IfValueTF{#2}{#2}{Default},%
  FontFace={sb}{n}{\FontName{} Serif Semibold},%
  FontFace={sb}{it}{\FontName{} Serif Semibold Italic},%
  ]{\FontName{} Serif}
  \babelfont[#1]{sf}[%
  Language=\IfValueTF{#2}{#2}{Default},%
  ]{\FontName{} Sans}
  \babelfont[#1]{tt}[%
  Language=Default,%
  Scale=MatchLowercase,%
  FakeStretch=0.8,%
  ]{\FontName{} Mono}
}

\DeclareOldFontCommand{\sbseries}{\fontseries{sb}\selectfont}{\mathbf}
\DeclareTextFontCommand{\textsb}{\sbseries}

\LoadFont{american}
\LoadFont{american}
\LoadFont{macedonian}[Macedonian]
\LoadFont{macedonian}[Macedonian]
\LoadFont{serbian}[Serbian]
\LoadFont{serbian}[Serbian]
\LoadFont{russian}
\LoadFont{russian}

\NewDocumentCommand{\SampleText}{}{бгдптѓ/}
\NewDocumentCommand{\TestItem}{mm}{%
\item[#1]
  \begin{otherlanguage}{#2}
    \begin{description}[widest=\FontName{} Serif]
    \item[\FontName{} Serif]\rmfamily
      \begin{description}[widest=Semibold Italic]
      \item[Regular] \SampleText{}
      \item[Semibold] \textsb{\SampleText{}}
      \item[Bold] \textbf{\SampleText{}}
      \item[Italic] \textit{\SampleText{}}
      \item[Semibold Italic] \textcolor{red}{\textsb{\textit{\SampleText{}}}}
      \item[Bold Italic] \textbf{\textit{\SampleText{}}}
      \end{description}
    \item[\FontName{} Sans]\sffamily
      \begin{description}[widest=Semibold Italic]
      \item[Regular] \SampleText{}
      \item[Bold] \textbf{\SampleText{}}
      \item[Italic] \textit{\SampleText{}}
      \end{description}
    \end{description}
  \end{otherlanguage}%
}

\begin{document}
\begin{description}[widest=MKD]
  \TestItem{MKD}{macedonian}
  \TestItem{SRB}{serbian}
  \TestItem{RUS}{russian}
\end{description}
\end{document}

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