They certainly want people to go to the muster station, because they have a duty to check that everybody is accounted for. Anybody who fails to arrive at their muster station within a reasonable period of time, will cause the crew to go searching for that person, and in so doing, put themselves and possibly the ship in danger as they will not be able to attend to other duties. All crew are assigned a duty to perform in the event of a muster or abandon ship situation.
As for not returning to your cabin to don a lifejacket - and instead go straight to the muster station - you may regret this later when your're sitting shivvering in a lifeboat without TPA (Thermal Protective Aids) ie. warm clothing. Also, at this point you may realise that you're without that essential medication you were instructed to take with you - and people dying from (Eg.) heart attacks in lifeboats does not exactly boost morale!!!
Actually, in real life, people do not panic and run straight from the sun deck to the muster station. They normally follow instructions (esp. when scared).
Re. The Watertight doors - You should have been mustered a long time before these doors close. But the answer to the question is 'Yes' if you get trapped between a set of these doors - you're trapped. My wife managed to get herself trapped for half an hour between these doors with several other people
despite the warning made several times that a water tight door test was going to be held on deck 5 at hh:mm.
In a real life situation, I suppose that if the ship was truly sinking and you got stuck between these doors for whatever reason - well - you'd probably live for a few minutes after the ship goes down - and the hull will probably implode under water pressure. Which is better than dying of suffocation over a period of two days. Nobody will attempt to rescue you as recovering the sunken ship even if possible - is going to take months - and there's no way for them to cut a neat little hole in that water tight section and hoist you out without getting your feet wet.
To avoid this scenario - best book a suite on a high deck. But hey, they're normally the more expensive ones. Now we know why.....