You actually do. All of those puzzle-style questions of the sort of "how many liters of water in Mediterranean" ask you to develop a solution with a vague requirement by leveraging what you know roughly to demonstrate you can specify requirements yourself (oh, Mediterranean is roughly 5000sqkm [-> I need surface area], on average 50m deep [-> I need average depth], this gives me A x B liters total) — I'd call these the leet-code version of requirement understanding/development.

But really, any interview is really about giving you a requirement, and seeing _how_ you understand it, how you clarify it with your stakeholders (interviewers), and then how you address them.