Events on a custom field of type Data triggers too soon

#1

I’m coding a client-side script in JS and have the follow event listener for the is_user custom field which is of fieldtype Data.

frappe.ui.form.on('PM Appraisee', {
    is_user: function(frm) {
        fApplyIsUser(frm);
    },
...

However this event triggers whenever there is a lull in editing the value of the field.
I would like the event to trigger only when focus is lost.

How can I achieve that?

#2

After a bit more investigation, I’ve noticed that master and child field events trigger differently.

Unlike on a lull, a child field triggers on lost focus, which is much more convenient.

 frappe.ui.form.on('PM Client', {
    // Field events trigger on a lull in editing, hence we have to rather annoyingly use the validate event
    // Be very carefull when using a field event as it can trigger multiple times during lulls in editing
    validate: function(frm) {
        fValidateEmail(frm);
    },
});

frappe.ui.form.on("PM KPI", {
    // We do not have a convenient way of applying a mask to the Goal field which is of Data fieldtype,
    //  hence we have to validate the string some time after it has lost focus
    // Unlike for master DocTypes, child table field events trigger on lost focus
    goal: function(frm,cdt,cdn) {
        fValidateGoal(frm,cdt,cdn);
    },
});

Is there any reason for triggering field events on a lull? Or is it so, so that any programmatic changes to the field will also trigger, not only a user editing the field? But then the same should apply to child fields?