There's also that a #1D in his prime is just about unmovable, so the only way it happens is if it's someone either older (Jeff Petry* today) or a kid with potential on a team with a lot of depth on D (Seth Jones when traded to Columbus), in neither case were they clear #1D in their prime at the time.
In 2016 Subban could've gone for Draisatl and other juicy bits (Nurse, pick #4, etc.), which kind of shows a #1D in his prime costs a fortune in assets, ie, more than Scheifele on his own.
*: Just an example. Petry wants to leave Canada and the Habs don't want a headhunter who prefers giving concussions to stopping goals against. So not proposing anything here.