HIG still mentions that placeholders should have an ellipsis
Placeholders can be phrased in the same way as labels. Alternatively, if the text field performs an action, they can be phrased as an instruction, followed by ellipses. For example: “Search for a city…” or “Write a message…”.
https://developer.gnome.org/hig/patterns/controls/text-fields.html#guidelines
However, they have been removed two years ago: GNOME/gnome-shell@95ebbb93 GNOME/gnome-shell!2568 (comment 1609631)
Edited by Ghost User