Why can't I avoid notifying attendees when updating an event?
While some calendar providers allow you to suppress notifications being sent to attendees when an event is changed, not all do.
This means any change may result in notifications, and so your application integration should account for them being sent.
Because of this, we’ve taken the position to not expose this capability through the Cronofy API. This avoids the possibility of situations where attendees do not have up-to-date details for an event, or worse no knowledge of it at all.
We feel that notifying attendees too much is much better than a situation where they do not know about, or have incorrect details for, an event.