but it is pretty easy to trigger it by rotating a little enthusiastically and I have never known our aircraft to drop a wing. This is not something I would have expected
What I saw in the video is totally predictable. For those who practice stalls at altitude, most seem to practice them as a power off entry. Also practice stalls at a full power entry, and hold the control inputs through to stall break. If held well, with appropriate use of rudder and yaw control, you'll get a decent pitch down and stall recovery. But if yaw is not carefully controlled, it's going to roll on torque. Even a C172 will do this if the pilot is careless, and it is a spin entry. The evidence is that it spun to the left from pitch up, slow flight.
Sure, if the landing has gone bad, go around. During any go around, your first job is to maintain flying speed, and accelerate to Vx, the Vy as soon as possible. There is zero need to be flying slowly at altitude, if flying with greater airspeed and less altitude can be done with consideration to obstacles. Keep it low, and accelerate. Even if there are obstacles, if there is any concern about clearing them, I aim for two thirds up the obstacle, accelerate as much as possible, then sacrifice some of the airspeed to pop up over the obstacle, knowing that I can lower the nose again once clear, and continue to accelerate to Vy.
As seen in this, and many other videos, climbing slower than Vy puts the pilot at increased risk of stall/spin, and not being able to achieve a safe glide in the case of engine failure.