What are the implications of the doctrine of necessarily-incidental?

Hogg has criticized the rationale for this doctrine (in Chapter 15.8(e)). In particular, he has trouble reconciling this doctrine with the necessarily-incidental doctrine (which he calls the “pith and substance” doctrine), which analysis stipulates that a valid provincial law may incidentally affect a federal matter. He observes that the latter analysis is applied more frequently than the former. He reluctantly acknowledges the “effort” in Bell Canada v. Quebec 1988 CanLII 81 (SCC), [1988] 1 S.C.R. 749 (“Bell 1988") to define the boundary between the two doctrines.