Nah, Lue is being wildly stubborn, he refuses to play their young guys who seem like they could be better defenders. He's obsessed with having spacing at all times even if it comes at the expense of defense.
You look at the Celtics playing all their young guys, then you see the Warriors doing the same and the Spurs, yet he refuses to play Osman and Zizic. With how bad their defense is he should at least give them minutes with the starting unit, but he doesn't mix and match because they're "rookies" even though both have been pros for years.