From my understanding, that’s correct. The rigid insulation is not ‘in’ the air gap, but it could make up a portion of it. So when answering if rigid insulation might be found ‘in the air gap of a brick veneer wall’, rigid insulation could be a correct answer, as it makes up a portion of the air gap, in the same way that ‘brick’ could be considered a correct answer as well.
This question is trying to assess two areas of understanding:
- choosing an appropriate insulation given a particular wall type
- general construction of a wall assembly with brick veneer
NCARB is likely to split these into two separate questions. As long as you understand why and how the wall assembly is created, I think you’ll have the knowledge you need.