Frame your answer around risk management: Waterfall reduces certain risks (scope uncertainty) while accepting others (late feedback). Show you understand the trade-off.
Strong answers identify valid Waterfall scenarios: regulatory compliance requiring documentation, fixed-scope contracts, hardware dependencies with long lead times, or projects where requirements are truly stable. Best candidates justify based on risk reduction and stakeholder needs, not personal preference.
Tests critical thinking and ability to challenge orthodoxy. In an Agile-dominant industry, can they think independently? Conversely, Waterfall purists who dismiss Agile are equally concerning.