If the POH for the Seminole does not contain an emergency procedure for double engine failure then ... a fail assessment, based on such a procedure, could be challenged.
A successful
outcome is based on
procedures and
skills, applied with correct
techniques.
An examiner will usually look for correct skills and techniques, as this is the primary purpose of attending VFR flying school. To put it another way, the difference between success and failure in VFR piloting is rarely down to procedure.
For specified items - e.g. emergencies - correct procedures will also be needed but the candidate usually can get away with justifiable variations. If a procedure isn't defined in a legally authoritative reference - POH, AFM - only skills, techniques and outcomes can be assessed.
Pass / fail judgement is based primarily on an evidence-based outcome. But by the time an outcome is certain, a competent examiner has already made up his/her mind based on quality of skill & technique.
Hence: "I'm sorry to say you have failed, as you could not have achieved your nominated field in the forced landing
(outcome). When re-training, you might like to review trimming to achieve a stable speed
(skill), which allows you to focus on flying accurately to a well-spaced low key position
(technique)."
Providing CASA has specified failing to make the field as a valid fail point in the forced landing exercise, it would be hard to successfully challenge that assessment. Note that the manufacturer's procedures don't come into it.