Different touch-up behaviour on pop-up than mutter
I havent looked at any wayland logs but accoring to Librem5/debs/webkit#16 (comment 162946) long press + release keeps the context menu in GTK open with gnome-shell/mutter but not with phoc.
I don't have a touch capable gnome-shell device atm so i've not compared wayland logs to figure out who's at fault here.
Fixing this would unbreak context menus in e.g. nautilus and other apps.