I hope this policy refers to a club test Jon, not the BMFA Achievement Scheme A test.
My understanding is that it’s an absolute requirement that the manoeuvres must be demonstrated to an acceptable standard. The examiner may ask a candidate to repeat an aspect which falls short of the required standard but only to a limited degree. Your pilot of known ability shouldn’t have any problem repeating the test if he messes up the first attempt if he’s at A standard. Accepting lower standards “because he’s usually OK” devalues the value of the scheme as it is not a true recognition of their achievement.