I have now booked 2 air trips with the Chase portal using points earned on this card for part of the airfare. In both instances there was a significant change to the flight schedule after I booked. That part had nothing to do with Chase. It was just chance. But, in both cases I was not informed by anybody and only found out when I visited the airline website (in one case American, in the other Delta), and saw the change noted there after I signed in and reviewed my trip info.
The problem seems to be that the airlines don't communicate with Chase in a way that updates the Chase travel system. Right now, on the pending trip, my Chase account shows my flight info as I originally booked. Meanwhile, the airlines also either can't or choose not to tell me directly. They say they don't get my contact info from Chase, but I also have accounts with both airlines and they have contact info from that and the flight info is properly associated with my account.
The bottom line is, my advice is that when you book with the Chase portal -- it is up to you to periodically check your itinerary on the airline site and see if there has been any alteration. For the first trip, the big change was our outgoing flight on a WDW trip was moved up to a 6am departure, which was extremely annoying but again, not really related to booking through Chase and there was no big negative effect from not finding out immediately. There weren't any alternatives to rebook for a more reasonable departure anyway. But on the pending trip coming up in November (not to WDW by the way) I had connecting flights that were changed so much that rebooking was mandatory because the connection became impossible. If I did not have other business at Delta.com this weekend, I do not know when I would have found out about the need to rebook and I might not have had any reasonable options. So again, if you use the Chase or any similar portal, check your reservations and itineraries on the airline site every 2-3 weeks just in case, because nobody will tell you when things change.
ETA: I received an automated telephone call from Chase on August 24, close to 3 weeks after I discovered the latest change myself. Now that this happened, I do think something similar happened the first time as well. So Chase eventually finds out and notifies me, but very late.