Flamespyre Phoenix question

[Azamar]

Regarding the phoenix’s wake of fire ability, does the Phoenix have to completely pass over the model/ unit I target, or can it just clip the target? 

For example, assuming it has enough move to do so, can it move up to a unit, clip over part of it, then move back until it is more than 3” away to finish it’s move, activating the wake of fire on the unit it clipped. Or should it might be in a straight line and completely pass over the unit?