Riding tandems off-road in technical riding locations teaches and almost forces you to learn skills that carry over to the road.
We are by no means any kind of highly rated circus act for skills at track standing, then again we are not like clowns that attempt and fall over. I am sure the right team can do this easily.
Off-road, there are many instances when we must virtually stop, then accelerate away. So the amount of time we can balance is fairly short.
Key word is practice, learn to accomplish it in running shoes before cycling shoes and clipped in. Consider also, most trackstand capable riders often turn the wheel 45 right or left, I always found this make the tandem a bit less controlled for us.
We are not good at trackstands, but work it into the ride whenever needed. Often ending with a foot down or very slowly rolling forward (1 foot or so) until the green light.
PK