Numbering broken with multiple refcontexts using same sorting

[sim642]

I'm trying to use multiple refcontexts with the same sorting, but different subsets of entries in various places (by refsegment). It seems that biblatex considers all refcontexts with same sorting options the same (even though each is a distinct local one) and applies the sorting from one to another. In the following, I haven't named refcontexts, but even when they are declared and used by name, the issue persists. Internally, it seems that biblatex just has one refcontext including dnt in the name, not two separate ones that can have entries printed in different orders.

Reproduction

LaTeX

\documentclass{article}

\usepackage[style=alphabetic,defernumbers=true]{biblatex}

\defbibenvironment{numeric}
  {\list
     {\printtext[labelnumberwidth]{%
        \printfield{labelprefix}%
        \printfield{labelnumber}}}
     {\setlength{\labelwidth}{\labelnumberwidth}%
      \setlength{\leftmargin}{\labelwidth}%
      \setlength{\labelsep}{\biblabelsep}%
      \addtolength{\leftmargin}{\labelsep}%
      \setlength{\itemsep}{\bibitemsep}%
      \setlength{\parsep}{\bibparsep}}%
      \renewcommand*{\makelabel}[1]{\hss##1}}
  {\endlist}
  {\item}

\defbibenvironment{itemize}
  {\itemize}
  {\enditemize}
  {\item}

\addbibresource{sample.bib}

\assignrefcontextentries[name=default]{*}

\begin{document}

\begin{refcontext}[sorting=dnt]
Some interesting things:
\begin{refsegment}
    \nocite{testA}
    \nocite{testC}
    \printbibliography[segment=\therefsegment,heading=none,env=itemize]
\end{refsegment}
Some more interesting things:
\begin{refsegment}
    \nocite{testB}
    \printbibliography[segment=\therefsegment,heading=none,env=itemize]
\end{refsegment}
\end{refcontext}

Bla bla bla~\cite{testA,testB,testC}.

\printbibliography

\begin{refcontext}[sorting=dnt]
\printbibliography[env=numeric,resetnumbers=true]
\end{refcontext}

\end{document}

Bibliography

@misc{testA,
    author  = "Test Alice",
    title   = "Test",
    year    = "2020",
}

@misc{testB,
    author  = "Test Bob",
    title   = "Test",
    year    = "2010",
}

@misc{testC,
    author  = "Test Charlie",
    title   = "Test",
    year    = "2015",
}

Actual output

Expected output

The numbering in last bibliography is 1, 2, 3; not 3, 1, 2.

If the first refcontext is not there, then the numbering in the last bibliography is correct, but then the entries in refsegments are not sorted as I want.