The water did shut off successfully. The pressure did pop off in a fraction of a second. Or, if you have a leak in the system, it disappeared in a couple of seconds - too fast for you to find a faucet and open it.
Why did it not run in the previous house? Because the water system was fully sealed, and vacuum locked. Water couldn't fall, because if it did, there'd be nothing to replace it. It would leave a complete vacuum (like the vacuum of space), and that requires 32 feet of "head".
Why is it running in this house? Because of the leak. Opening a lower faucet means you now have two openings in the water system - the opened faucet, and the leak. Air is now backfeeding through the leak at a certain rate, and water can fall only that fast. That's why it's taking a long time to empty.
There's one more reason it may seem to take a long time. Water main valves are rarely operated, and so they often "mineral up" to where they can't completely close. So even with the main closed, water will keep seeping into the system. If you're trying to solder, those are tough.