I see your point mate, I really do.
But in the real world of MOT testing we have only 45 minutes maximum to actually test the vehicle, we can not go past that time frame.
So bear in mind that if an examiner is in any doubt to wether a car had original equipment fitted or not, it means a trawl through the VOSA manual "which is limited in it's comprehensiveness" and then resorting to either emailing them for clarification OR calling the helpline, which takes a minimum of 15 minutes to get through the automated system of number punching the chassis number etc... So then we are left with a maximum of 30 minutes to complete the test...
Fortunately, VOSA/MOT want the vehicle to be safe first and foremost with suspension/tyres/brakes/ seatbelts/ structural integrity and relative pipework as THE prime directive... Then ancilliary parts like lights /mirrors/ horns... So where does that leave us in a practical sense?
That's exactly why they leave it to the examiners discretion within the testing proceedure and experience to know if a CAT is actually required.... Not ideal but, that's the crux of it, time frames must be adhered to in order to preserve "fairness" apparently!
Any mechanic/ mot examiner can find many, many more minor faults given time to do so but......
It's all well and good a VOSA technician sitting in a VOSA test bay being able to do a full examination with all the relevant information directly to hand, all within 45 minutes.... Unfortunately 99% of approved testing stations don't have that back up or support and have to rely on a "line busy" phone call for clarification.... Never perfect but in the eyes of VOSA, it works!