Hi -
You can allow your promoted properties to also be "demoted" - that is, you can change the value in the library item instead of having to actually open the form.
So, if your form had logic on the "Phone" field - a rule to clear another field for example - but you allowed users to change that field in the library (either in data sheet view or by editing the item properties), the logic on the field wouldn't run because the data wasn't changed from within the form. Does that make sense?