Ok... I did the fault finding test last week and it was 4 columns of data, a name, a number, a code and an area (broadly speaking). There was then also an asterix which was present on one column, but it kept jumping around. The asterix denoted a seperate process of referring to a "key" of priority. So for each example you had to cross reference 4 boxes of numerical data, then identify the asterix to work out the key and whether that was correct or not, then once you had worked out which of the 4 columns were wrong (any combination) or if NONE were wrong, you had to work out which answer was correct as it lists all possible combinations. So this takes a fair bit of assessment for each question. If you are doing that accurately in 10 seconds or less for each question then you must have some form of super power. I have a neuro diversity which I find helps me do tasks like this, I am pretty swift at tasks such as this and I have passed the fault finding test to enhanced level at another TOC (a dials and pressures test where I completed 43/45 questions).
I found the GWR one particularly difficult mainly due to the key which was constantly changing for each few questions. Of the group of people that I did it with we all said the same thing about how tough it was, and half of them didn't get through.
I see what you are saying about if you are use to checking spreadsheets then it would be an engrained skill, I don't work with them at all however - and what is the link with spreadsheets and train driving - routes / signs? I have worked in a safety critical industry (that my DMI interviewers said was more safety critical than the railway) for just under 30 years and have a great deal of experience of signature, maps, diagrams and processes - but this spreadsheet test was certainly tough for me.