The assessors aren't trained educators; they are nurses who are on shift and have their own duties to attend to. That's not an easy job, and it takes a lot of patience and understanding.
When I was a carer, part of my job as a senior was to train new carers. I was always open with my manager that I hated training people and was rubbish at it, and she knew to take my opinion on someone's capability with a pinch of salt.
It wasn't up to me to pass or fail anyone, but my opinion as a senior was taken into account when assigning shifts and deciding who was capable enough to be on the long busy shifts and who needed to be on the short shifts, who are only there to support the long shifts through the busy periods on the rota.
I especially hated training people on night shifts. They were busy, understaffed shifts with no leeway in timings, and trainees were there instead of an experienced carer, not as an extra pair of hands, so I wanted trainees to take on the easy tasks I assigned them, then stay out of my way and let me do my job. I didn't want them asking questions, needing support, or making mistakes.
Out of the dozens of carers I trained, I gave positive feedback on one carer. The rest ranged from meh to "put me on shift with them again, and I will hand in my notice." The common theme in the lack of capable carers I was assigned was me, not the carers, and my reluctance to find the time to actually train them.