5 symbolic icons not taken into account

Context:

Use an icon theme having:

The following colored icons:

• help-about
• help-browser
• utilities-terminal
• preferences-system
• preferences-desktop-wallpaper

The following black&white symbolic icons:

• help-about-symbolic
• help-browser-symbolic
• utilities-terminal-symbolic
• preferences-system-symbolic
• preferences-desktop-wallpaper-symbolic

Steps:

1. open Thunar
2. Click on menus File, Edit and Help and left-click to display context menu.

Actual result:

The colored icons are displayed

Expected result:

The b&w symbolic icons are displayed

The icons:

For some reason, the bug tracker is unable to preview utilities-terminal-symbolic. This is the SVG code of that icon:

<svg width="16" height="16" version="1.1">
 <path d="M 3.71875,4 3,4.6875 5.625,7.5 3.03125,10.3125 3.71875,11 6.6875,7.84375 7,7.5 6.6875,7.15625 Z M 7,11 v 1 h 4 v -1 z" fill="#363636"/>
 <path d="m2 2c-1.108 0-2 0.892-2 2v9c0 1.108 0.892 2 2 2h12c1.108 0 2-0.892 2-2v-9c0-1.108-0.892-2-2-2zm0 1h12c0.554 0 1 0.446 1 1v9c0 0.554-0.446 1-1 1h-12c-0.554 0-1-0.446-1-1v-9c0-0.554 0.446-1 1-1z" fill="#363636"/>
</svg>