To answer your original question, I think the lust for a tall receiver comes from their ability to high point balls thrown above everybody else. The prototypes for this kind of tall receiver, most of which are also big, would be Marques Colston, Roddy White; and TEs, Jimmy Graham and Rob Gronkowski. They can get jump balls that DBs just can't get high enough to reach.
Receivers around 6', the size of DBs, can't jump any higher than the DB, hence the jump ball is up for grabs. Big strong, but not tall receivers, like Bolden can take the ball away from the DB because of their superior arm and hand strength and the ability to box out the DB with their body.
Little receivers, don't have to fight for jump balls because they get separation out of their breaks.
With Walker gone, might be time to draft a tall TE.