Do not try to prove both branches at once. Choose the branch with the strongest expected impact or the fastest discriminating test and explain that logic.

Interviewers usually care more about prioritization than perfect certainty. A reasoned choice is stronger than hesitation or exhaustive coverage.

You can say that both matter, then select one because it is larger, more uncertain, or easier to validate with available data.

If the first branch does not explain the issue, explicitly return to the second. That shows controlled iteration rather than tunnel vision. For a related reference, see When Should You Use Each Consulting Framework?.

I had the same concern before recruiting. Once I practiced the exact situation a few times, it felt much less awkward.