You've been taught the bog standard "East Anglia method". As you say, it goes like this:
- set up a circuit
- work out which field you're going to land in
- point it out to the instructor or examiner.
Provided your instructor or examiner is familiar with the "East Anglia method" this works fine. If they come from a different part of the country, and are more concerned with the rule book than whether you're going to survive, you point out to them that the pass-fail criterion is not "would he have made it to the field he designated from 3000'" but "would he have walked away".