Hello again,
Can't remember if there are other forms for the CRM ContactNote BO but if there is, it's possible the form you are opening up is opened via a non default action for example if the form is opened up through a process, from a query etc. (If a form is specified in for example a process, this supersedes the default action behavior).
I am not sure this explanation above is the cause, it might be something else. The applicability functionality to my knowledge works as it should. Try this on some other BO form and see if that works (doing it right etc.?).