Shape of beta (β) in greek

[Doc73]

As you can see, two different beta are printed according to the language, but the convention is to print ‘curled’ beta (U+03D0) in medial position. It would also be possible to leave the ‘curled’ beta only as an alternative.

Thank you so much in advance.

% !TeX encoding = UTF-8
% !TeX program = xelatex

\documentclass{article}
\usepackage{fontspec}
    \setmainfont{Garamond Libre}[Numbers=OldStyle,Ligatures=TeX]
\usepackage{polyglossia}
    \setotherlanguage[variant=ancient]{greek}

\begin{document}    
    βάρβαρος

    \textgreek{βάρβαρος}
\end{document}