According to 'break it down', it takes about 33/34 seconds to sing and dance across the bridge. This makes the reason for the lack of a bridge from Auradon to the isle more clear - Because if there was a bridge there, and the villains managed to break or get through the barrier, then they would be able to get to the mainland in less than 30 seconds based on this. So the Council deciding to break or disappear the bridge so it couldn't just easily be used makes sense. And the villains who can fly, teleport, or have access to a boat could just leave if it was broken, but the villains who don't have those things would be stuck there, at least. So I believe it's something they would consider.
The golden bridge still appearing when leaving without the remote having to be pressed a second time is a possibility, and one I think is true, but maybe only happens in certain situations, like if just a hole in front of the bridge is opened.