That's right - if an event appears under aerodrome notams only, then a narrow route briefing will not pick it up.
And it is not reasonable for a pilot flying A to B to seek aerodrome briefings for airfields along his route. That would be completely nuts; not even the most diligent pilot will be doing that and it isn't the way the notam system is supposed to work. If this really was needed then the notam was filed incorrectly.