We do national obs courses too.
It doesnt help when there are NO national guidelines to follow. This leaves the whole process wide open to challanges from the onset!
However, with the case in question:
IF student B fails on safety and obstruction reporting and this alone, then I'm afraid he has our full support in complaining. It is NOT his/her job, full stop. It's nice to have the back up and we employ this tactic to afford the observer more responsibility.
When we select a candidate to join us, we are looking for a rounded person, not just an expert in one small area. If they have the general aptitude to tactically think in the air...that is what we want. We orientate our checks and measures therefore to weed out the weaker candidate. It would however amount to a series of 'black marks' across several check areas before we failed them totally. This also leaves us less exposed to any failed candidate who chooses to challenge our findings.
At the end of the day they are after all - passengers!