Keep in mind that a commercial glass shop would not produce a single item at once. The economies of scale (just as true in those days) and typical layout of a glass shop meant that they could easily and more cheaply produce several lines at once. The basic resources (a pot of glass and a glory hole) can be used by multiple gatherers, finishers and helper boys at once. A good shop has a ballet-like timing where they are doing their tasks among shared shop resources without getting into each other's way. Cane construction is probably the most time-consuming task that requires 3-4 people for a bit.
There isn't anything in a small hot glass shop that would suggest that specialization offers a benefit. In the end - shops are filling orders from wholesalers.