First, your logic assumes that "pledged delegates" is some kind of colloquial term being tossed around by news networks, to be defined in the manner making the most sense to you, when in fact it's a formally defined term for what you called "electorally chosen delegates". That was what I was originally commenting on w.r.t. your comment.
However, since you ask for further argument, the differences between pledged delegates and superdelegates are quite important. First, the odds of a superdelegate actually changing their vote before the convention are higher than the odds of a delegate voting against their pledge at the convention. Second, superdelegates don't follow proportional allocation, so Bernie doesn't need to make the same proportional-math comeback in superdelegates to swing the superdelegate vote. Third, as I've said previously, while superdelegates have *counted* in previous primaries, they've never decided the primary. Superdelegates are perceived as the arm of the party establishment (and let's be real, they are), and if the party establishment is perceived as fucking over the pledged delegate vote to put their anointed insider on the hot seat, voters will go bananas.