Hi, @courrier!
You have almost answered your own question. The most suitable icons for the cc and sh processes have been chosen from your icon theme.
~$ find /usr/share/icons -type f -name cc.\*
/usr/share/icons/Yaru/scalable/status/cc.svg
/usr/share/icons/mate/scalable/animations/cc.svg
~$ find /usr/share/icons -type f -name sh.\*
/usr/share/icons/Yaru/scalable/status/sh.svg
/usr/share/icons/mate/scalable/animations/sh.svg
To better understand the general idea, the icon lookup mechanism is documented. However, the exact implementation of these algorithms for GTK-based desktops is in the GTK library.
The easiest, but somewhat dirty approach to fix the problem is to modify your icon theme (similar to the UN logo issue).