As per https://kb.blackbaud.com/articles/Article/118291, CUB updates the Date Changed field for phone numbers, email addresses and addresses which didn't actually change.  This is then misleading when we query on or manually look at records.  This is misleading for reporting, detecting changes for integrations, or simply manual troubleshooting by our Supporter Care staff.  Please fix the system so that the date is only updated when there's an actual change. 

In programming this, presumably it could be done by using some sort of 'dirty' flag or by comparing the value which was to be saved with the value already on the record, and not saving the new value if it was the same as the existing value.