I haven't found anything in writing but was told by the Titanium call line that Titanium Elite status allows one to cancel a reservation the day of check-in. We changed a reservation within 24 hours of check-in, effectively cancelling that reservation, and changing the check-in date and check-out dates for a 15 night stay we arranged for our son and his family on Bonvoy points at a Residence Inn. The call line was incredibly helpful; the initial email confirmation for the reservation said we could cancel or modify 2 days prior to check-in (and we were already pass that date when we changed the reservation with the call line).
Another thing that isn't mentioned in writing anywhere I could find is that I was able to book this reservation in the name of my son and his wife on Bonvoy points. In the past, when booking for someone else using points, I had to go through some additional procedures as I recall. In this recent case, I just booked the reservation over the Titanium call line in the name of my guests, who were also able to use my status for an upgrade. This was an emergency situtation for us and it worked out well for us.