I don't like Harris at all and certainly not at that money.
And I'm not sure where this notion came from that he is this super efficient scorer. His 2PT% is barely 50% and his 3PT% is just 36.7%. Those aren't terrible, but they aren't great either. And isn't like he got to the line a ton at just 3.6 a game. 1.22 points per shot doesn't scream super efficiency to me (DeMarre Carroll for example was at 1.35 points per shot, that is a much better efficiency).
He is young and will likely get better, but he isn't a move the needle type of player, so I don't really see the point in giving him a max contract, which is why Orlando is letting him go.