WSIM in this site differ "a lot" from the official game. There are missing things and changes.
Some changes are necessary to allow the game to be as quick and funny as possible. For example when two enemy ships are at the same distance from your firing ships you are NOT asked to which ship you want to fire. To change this means stopping the game sequence to ask the player what to do, and that would cause a long delay.

At the moment there are many missing things like drift, wind change, different ammunition, melee, transfer boarding party, anchor, land, shallow exes and all advanced rules. Some will be implemented as the official rules mandate but most not. Another reason to make differences is to simplify (1) the coding effort and (2) the user interface. The code should be kept as simple as possible because simpler code is safer (less bugs) , more maintainable and take less time to be produced (more interesting features or different games instead of a 100% precise rule). In some case a more complex user interface could allow the player to decide more (for example to give the list of preferred targets in the case above of same distance targets) but we feel this game is already very complex for most players.

What is really missing is a strategy guide and a "how to play" interactive tutorial (I like vampiring ones, do you?).

About your specific question, if I remember well, the collision mechanisms is the only not evident thing that is changed with respect to the official rules.

If you check this post http://www.youplay.it/beta/play/forum_showmessage.asp?msgid=2430
you find a list of new features that Nick is developing.

We do not intend to invest much time on rules revision (too many things to do, too few time available) but of course if there are volunteers out there.... they are very well appreciated.

ciao have fun
alex

To change this means stopping the game sequence to ask the player what to do, and that would cause a long delay.