He repeated this several times. It is important, particularly when experimenting with new ideas, to take care to make sure that we are seeing what is really going on, not only to not miss small gestures and communicative attempts, but also not to overestimate. Over-estimating can be as damaging as missing something. That also produces inconsistency, and can cause confusion. It is also important to learn to observe closely and carefully.
Observation is helped by recording evidence , giving confirmation of each small step of achievement.
It is also helped by being shared. Where the observations were shared by two adults there was a greater confidence, both in believing what was seen, and in designing and modifying activities. This is not easy. It takes time and, above all, perseverance. But the rewards are worthwhile, and our pupils have a right to them.