Help nit (FFIND and DIR with /S)

[vefatica]

For both DIR and FFIND, the help for "/S" mentions only "the current directory and all of its subdirectories". But there's a very useful (and old) behavior wherein if file contains a path then that path is used as the root for recursion. For example,

v:\> dir /s /f g:\tc21\4u*
G:\tc21\plugins\4utils.dll
G:\tc21\plugins\4utils.dllxx

v:\> ffind /s /a:d /h g:\tc21\*
G:\tc21\Assets
G:\tc21\plugins
G:\tc21\styles
G:\tc21\plugins\hold
G:\tc21\styles\Distrib

Is there a way one might discover that behavior? I looked (only a little) and didn't find one.