Symbols from Symbol Library are always interpreted in px (but stroke-width in mm)

Summary:

With default Inkscape document settings, the stroke width of a symbol from a symbol library file is interpreted in mm but its other dimensions are interpreted in px.

Steps to reproduce:

• Insert the symbol contained in the minimal symbol library file below into a Inkscape document (default settings).

<?xml version="1.0" encoding="UTF-8"?>
<svg
   version="1.1"
   xmlns="http://www.w3.org/2000/svg"
   xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>Test Library</title>
  <defs>
   <symbol id="testsymbol">
      <title>Test Symbol</title>
      <path
         style="stroke-width:1;stroke:black;fill:none"
         d="m 0,0 h 10 v 10" />

   </symbol>
  </defs>
   <use x="0" y="0" xlink:href="#testsymbol"/>
</svg>

What happened?

The symbol displayed in the document has stroke-width of 1mm but its size is 10px by 10px (not counting the stroke-width).

What should have happened?

The symbol should be 10mm by 10mm (not counting the stroke-width) instead of 10px by 10px.

Version info

Inkscape 1.1.1 (3bf5ae0d25, 2021-09-20)

    GLib version:     2.70.0
    GTK version:      3.24.30
    glibmm version:   2.66.1
    gtkmm version:    3.24.5
    libxml2 version:  2.9.12
    libxslt version:  1.1.34
    Cairo version:    1.17.4
    Pango version:    1.48.10
    HarfBuzz version: 2.9.1
    Poppler version:  21.08.0

    OS version:       Windows 10 2009