OnePlus 5 and 5T latest update enables Treble support
OnePlus 5 and 5T, and even though it's not mentioned in the changelog, the update does bring the promised Project Treble support. Although this isn't a consumer-oriented feature, it does help developers and handset manufacturers send software updates faster.
If you've already installed the new OxygenOS 5.1.5 update on your OnePlus 5 or 5T, then your smartphone now features Project Treble support. Aside from that, there are a few other improvements included in the update such as the option to confirm PIN without tapping √ to unlock the phone (Settings / Security & lock screen / Screen lock / PIN).
Also, the 1.6GB update adds the August security patch, the most recent security update released by Google. If you did not receive the update yet, give it a few days since this is a staged rollout.