U-turns are not perfectly safe. Last week I saw a U-turner almost a hit a biker as they backed up after not being able to complete the turn in one pass. Can they be done safely? Sure. But that's not the same as perfectly safe.
Perhaps the phrase “perfectly safe” is wrong. Maybe “otherwise intrinsically safe” would be more accurate. Having said all that, I do wonder if we have U-turn accident statistics.
That's no longer a U-turn