GTK/icon theme reverts to Adwaita after restarting gnome-shell

Affected version

gnome-shell 3.36.0 Arch Linux XOrg

Bug summary

When running gnome-shell under Xorg, with a non-default gtk theme selected in gnome-tweaks, the theme is not maintained across restarts of gnome-shell with alt-f2 + r

Steps to reproduce

1. In gnome-tweaks, select a custom theme (I'm using Yaru-dark)
2. Press alt-f2 and enter 'r' to restart gnome-shell

What happened

New GTK windows opened after restarting gnome-shell have the Adwaita theme. Existing windows remain with the old theme. Switching GTK themes in gnome-tweaks has no effect on any windows. Same seems to apply to the icon theme. Custom shell theme is maintained, however.

What did you expect to happen

GTK theme should remain as it was for newly-launched applications. Changing the theme should affect all running and future applications.

Here is a screenshot after setting the theme to Yaru-dark, then restarting gnome-shell, then opening gnome-tweaks and setting the theme to Arc-Dark. Chrome remains themed with Yaru, gnome-tweaks is themed with Adwaita, and setting the theme to Arc-Dark had no effect.