Being 6'8 is the special part? Luka is 6'7, so where does that leave us? I can't discount all that Harden, Kobe and Wade do because they're a couple of inches shorter. They actually player more comparable roles to Luka.
Luka is the primary ball handler for his team. George is not asked to do that, although he handles the ball very well and would be fine if a team told him to play point forward. George plays a true SF role who sometimes plays 4 in a small ball lineup. That does not lend itself to getting a bunch of assists as easily as being the actual point guard on a team. In addition, he is playing alongside Westbrook who is absolutely ball dominant and yet PG is still putting up similar assist numbers to Luka. As a matter of fact, George just posted a triple double yesterday. And he can defend his position. You asked me about 6'8 wings, so I gave it to you.