Trump's ultimatum and shifting deadlines: what makes them different?

A new deadline is fast approaching in the Iran war as U.S. President Donald Trump warns Tehran it must reopen the Strait of Hormuz by April 7 at 8 pm Washington time or face sweeping military strikes. At the same time, Tehran has delivered a 10-point response to an earlier proposal signaling little willingness for a temporary ceasefire and instead calling for a broader, more comprehensive deal to end the war. What makes this ultimatum different? How should we understand the U.S. threats against civilian infrastructure in Iran? Are we heading toward a breakthrough or a dangerous turning point?