SmartGWT and global ID clarification

I have a DynamicForm with a global ID (form.setID('myForm')) which is a member of a VStack. However, if I call vStack.removeMember(form) the form disappears but the global ID is still available via JavaScript-Console and the form still seems to exist.

Is this the correct behaviour? Does the form get cached? Can/Should I manually destroy the form to free the ID?

Thanks
Krigu