Of course there can be such a thing as a labor shortage, under many different scenarios (during sustained high rates of real economic expansion, specialized types of labor that are difficult to train enough of, fading-away segments that aren't being replenished with new labor due to lack of interest (yet still require active labor), not enough manual labor, not enough immigration, not enough population growth, and so on).
Low wages can make a labor shortage worse, is the actual context.