On a wide road in Groningen you want to turn left; an oncoming car also wants to turn left, but has already clearly committed to passing in front of you instead of 'left-past-left'. What do you do?
You adapt your manoeuvre to the oncoming driver's visible position, not blindly to 'left-past-left'
You stick to 'left-past-left', because that is always the rule for two left-turning cars
Explanation
Wrong — trap: exceptions ignored. If the oncoming driver has already clearly committed to a position, the 'left-past-left' main rule no longer applies (Book p.139).