Not a bug. bidi package has a boolean \if@Latin. The boolean should be set
in higher level packages (like polyglossia) to true for non-RTL scripts and
false for RTL scripts. Its initial value is false so that explains the
behaviour.
Therefore
\documentclass{report}
\usepackage{amstext}
\usepackage{bidi}
\makeatletter
\@Latintrue
\makeatother
\begin{document}
V $_{\text{[high, low]}}$
\end{document}
works as expected.
Note: I did not need to load biblatex package unlike you.
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