Our software follows the recommended design model as advised by Microsoft at the time. Programmer's expectations have changed to some degree since then, especially with most internet style applications providing actions on such events as listbox changes, etc. But so long as we don't break backward compatibility it shouldn't hurt to offer more events (where it is worthwhile to do so).
The open/close options of Screen Builder follow the same procedure, as far as we are aware, as if you were using Microsoft Office. Cancelling a Word document or cancelling changes in the Screen Builder present similar prompts and consequences. It seems sensible to us to follow conventions that most users would be familiar with.
You're welcome to post any comments you wish, although when we get into 'nitpick' type feedback, then of course the best approach is to some degree a matter of opinion.