Almost all search entries don't have a placeholder

From the following sections:

• Main window
• Applications panel
• Printers panel
• Keyboards panel: Add an Input Source dialog
• Keyboards panel: Custom Shortcuts dialog

In both focused and unfocused states, some search entries don't have any placeholder:

The same problem happens in Initial Setup, for example: gnome-initial-setup#144 (closed)

I've seen this in a lot of libadwaita apps and it seems that placeholders are optional, because some search entries do have them:

However, the placeholder could be available by default in all search entries, because only relying on the search icon might not be accessibility-friendly. The lack of a placeholder also might not help inexperienced users.

I'm also unsure if I filed the issue in the correct issue tracker. Perhaps it should be at @Teams/Design/hig-www?

Additional info

• libadwaita-1.2.0-1.fc37.x86_64
• GNOME/GNOME Settings 43.1
• Fedora 37 Workstation