I just don't agree with that.
Gerald Green is a very athletic wing that can do several things. Offensively, he can run the court, he can drive to the hoop and is a decent 3 point shooter. He is a good rebounder for his position as well and can contest shots with his length and hops (if he is there on time).
Copeland is a very different player. He is an unathletic forward with decent size and length. Offensively, he is a very good 3 point shooter that understands offensive spacing. He is also a decent passer and can score inside as well (he possesses some nice moves in the post). Defensively, he is slow and leaves a lot to be desired on the perimeter but he has decent strength and can push in the post. He isn't a good rebounder for his position, though, due to his lack of athleticism.
They are just nothing alike. Green relies a lot on his athleticism while Copeland relies a lot on his shooting touch. They are just different players.
The only common denominator is that thus far both of them have missed a few 3s.