I upgraded to Ubuntu 18.04 prerelease from Ubuntu 17.10 and am finding that Nautilus searches all subfolders when I start typing, not just the present folder, even though I have the "search only current folder" option selected in its preferences, and "Only searching the current folder" does appear in the GUI as I am searching. Nonetheless results appear from subfolders (which I wouldn't mind, but which I turn off due to its poor performance compared to current-folder-only).
I upgraded to Ubuntu 18.04 prerelease from Ubuntu 17.10 and am finding that Nautilus searches all subfolders when I start typing, not just the present folder, even though I have the "search only current folder" option selected in its preferences, and "Only searching the current folder" does appear in the GUI as I am searching. Nonetheless results appear from subfolders (which I wouldn't mind, but which I turn off due to its poor performance compared to current- folder- only).