After update, KDE Plasma identifies Tor Browser Nightly window group as "firefox-nightly"

Summary

Under normal conditions, KDE Plasma identifies the Tor Browser Nightly window group correctly (as "Tor Browser"). However, after Tor Browser Nightly installs an update and restarts itself, KDE switches to identifying the window group as "firefox-nightly".

Steps to reproduce:

Install Tor Browser Nightly into KDE Plasma X11. (I didn't check Wayland or non-Plasma environments, so no idea if it's reproducible there.)
Run Tor Browser Nightly and create multiple windows, so that Plasma collapses them into a single window group.
Observe the name of the window group.
Wait for an automatic update to be available. (Should only be a few days since Nightly is updated often; you might be able to speed it up by intentionally downloading an outdated Nightly.)
Allow Tor Browser Nightly to restart itself to install the update.
Create multiple windows again.
Observe the name of the window group again.
Exit Tor Browser Nightly.
Launch Tor Browser Nightly again.
Create multiple windows again.
Observe the name of the window group again.

What is the current bug behavior?

The window group is labeled as "Tor Browser" before the update, and "firefox-nightly" after the update. It reverts to "Tor Browser" after restarting manually.

What is the expected behavior?

The window group should always be labeled as "Tor Browser" (or perhaps "Tor Browser Nightly").

Environment

Debian Bullseye, KDE Plasma, X11. Installed Nightly from official download.