Practise. Test Kl. B / Do you have to drive with gear to the red traffic light ?

Hello Motor-Talk-Gemeinde, my wife and my stepsohn come from Ukraine, have had a driving license there for years incl. driving experience and now have to do the German driving license B (rewrite). You have to do “only” the Teoretic and practical exam B. Theory already done, now comes the practice: Today both have driven with a driving teacher. This then said that both have to take many hours to learn to drive with gear to the red traffic light. The old A utos in Ukraine go out if you leave the gear in it. Of course it is better if you uncouple “in the last moment”, but is this also relevant to the exam ?? Is there a law that forbids you to take the gear out before ????? Info would be great !!!