it improves the reliability of syncing mail, contacts, and notes with Exchange accounts
Since this is used by a lot of people, do we know what improvements?
Some of my family members have Exchange Online with tens of thousands of messages in their Inbox (default server policy moves anything older than 2 years to the Online Archive store).
For a long while now, these members' iOS Mail has been slow to launch. It takes seconds to open and load their Inbox. And they always upgrade to the latest iPhone.