Clarification for rotating after being tractored and moved by the opponent

[脸黑的饿货]

It is said in the Rules Reference that - 

A ship is tractored while it has equal to or greater than a specific number of tractor tokens, according to its size: a small ship requires at least one tractor token, a medium ship requires 
at least two tractor tokens, and a large ship require at least three tractor tokens. A tractor token is a orange token.
The first time a ship becomes tractored each round, the player whose effect applied the tractor token may choose one of the following effects:
• Perform a barrel roll using the [1↑] maneuver template. The player applying the effect selects the direction of the barrel roll and the ship’s final position.
• Perform a boost using the [1↑] maneuver template.
This move can cause the ship to move through or overlap an obstacle. After a ship is moved this way, if an opponent moved it, the ship's player may choose to have the ship rotate 90˚ to the left or right. If they do, the ship gains one stress token.

In yesterday store event some new guys argued about the explanation of "a ship is moved this way", so I come and ask for clarification.

When a ship becomes tractored for the first time in a round, it may gain 1 stress token to rotate 90° to the left or right, if -

a) It is moved by the opponent;

b) It is moved by the opponent and unfortunately moves through or overlaps an obstacle.

We usually resolve the situations in the way of a), but want it clarified to be right, since someone still believe that "a ship is moved this way" refers to the sentence right before it, rather than "This move" caused by the game effect of being tractored.

[Dee Y]

Interpretation a) is correct.  Whenever an opponent tractors you and causes you to barrel roll or boost, you may choose to rotate 90˚ and gain one stress token.  Whether or not you overlap an obstacle is irrelevant.