[tlhIngan Hol] The {-wI'} and the {-lu'}

Whenever we place the {-wI'} on a verb, we produce the meaning "one who does/is, thing which does/is". So, if we write {vumwI'} then we have the meaning of "one who works". But if we wrote instead {vumlu'wI'}, then we would seemingly/apparently get the meaning "someone (unspecified) who works". So, the conclusion here is that "the {-wI'} used on its own, talks of someone specified, while the use of it in conjunction with {-lu'} talks of someone unspecified" ? qunnoq