How are "Applications" run with krunner managed wrt processes?

I have a bash script, called runthunderbird, that… runs thunderbird :

#!/bin/bash
sleep 5
thunderbird & disown

When I execute `runthunderbird from krunner, Thunderbird starts after 5 seconds as intended, then the runthunderbird process ends, as evidenced by ps -ef` or the process list in the System monitor from Plasma 5.27.10. However, the same System monitor has an Applications tab where `runthunderbird remains listed, instead of thunderbird-bin`, with the resource (eg. memory) consumption of Thunderbird. If instead of just Thunderbird, the scripts runs several graphical applications before ending, they are lumped together in the Application tab, again under the name of the (terminated) script. I am wondering how this is managed and how I should write my script to completely detach thunderbird from the script than runs it. I am also wondering if this fact is related to Thunderbird not being effectively run when the runthunderbird script is run at login from a desktop file in `~/.config/autostart`.