While the first tick of the MoveFirstHalf child would run at the parent Move tick (see 2nd-to-last line in Move.Tick), this was not the case for Turn.
As a result, this Move tick would get wasted if a Turn was necessary, which at least contibuted to that visible jerk at the end of each L-turn (actors usually don't have the exact facing needed for the next move at the end of an L-turn).