Calling Harris a floor spacer is a bit of a stretch.
He shot below league average on 3's last year and only made 1.3 per game. For context, Stewart gets criticized for only make 1.5 3's per game. Harris only made 1.3 per game last year. He doesn't shoot it well enough or on high enough volume for defenses to really care about him.
I also don't see teams giving up picks to obtain him. He played 35+ minutes a game in the playoffs this year and couldn't even average 10 points per game. Teams looking at playoff runs don't want that.