However, the most important bit about it is the added support for OnePlus' Type-C Bullets Earphones. Up until now, OnePlus 3 and 3T couldn't output audio through their USB-C connectors. Unfortunately, the changelog doesn't say anything about third-party USB-C headphones, but we assume those are supported too.
To test them out, we've plugged in the OnePlus Type-C Bullets into a OnePlus 3 phone that's been laying around in the office, but to our surprise, the phone didn't recognize them. The earphones worked on other devices but refuse to play on the OnePlus 3 before and after the update. And there's no toggle in the settings menu either.
Of course, it could be a unit-related issue. Have you tried them out with the new update?
Seems like you have to enable OTG storage option under Settings>Advanced>OTG Storage and only then the type-c bullets are detected.