It shouldn't have. It will use the default if not specified.
Didn't have any impact, I'm afraid
It aren't easy to to keep up with the Gnome teams eradicating useful commands. I also try .icon-grid
The new black in inspector is "looking glass" in GTK4 - simple alt+f2 and write lg ... but it's harder to find what you're looking for.
I suspect that overview-icon is the issue. Part of the trouble of me not using GNome is my inability to simply go look for something...
I know that overview-icon was used in Gnome3+ for when a text label was carried but after Gnome4+, that class was removed.
BUT... I understood this was because they also removed the Text Label itself. Meaning that there is no over-view icon class (instead they use sticon for symbolic icons) and no label.
In Looking Glass, search show-apps and inspect its children.
You might see stbutton or sticon - Unless something has changed, I do not believe you will see st-label but happy to be wrong...
EDIT:
Try the .app-well class instead of .show apps class. Looking into documentation, that carries the overview...: