I find this statement very confusing.
Typically I'm looking for files in subdirs because I'm not aware of target's path. That's depth first (though of couse there is a change I'm going to find my target quite close to the starting point).
And if I'm looking in the same dir I'm currently in (or I know what dir to look at) - then there is no need for a sophisticated search anyway, as typicall you don't have too many files in a directory unless this is some kind of tmp or cache directory.