And just another point on “turns”. Of course, all the suggested durations are abstractions, and as in many rpgs, they are (in my opinion) a bit too long. But they ARE easy to remember, and easy to scale into narrative. You are right it only takes seconds to move across two zones (in fact it takes just one round). But stealth mode represents a different narrative, as seen in the movies - an individual or team stealthily creeping through spaces, finding their way, looking for things while all the time jumping at every shadow.
But in summary zones are a narrative abstraction to speed up play, not a tactical simulation.