Two days following the release of third developer betas for iOS 11 and tvOS 11, Apple has pushed out a third beta for watchOS 4, featuring a build number of 15R5321h.
The release notes for this latest beta, which is not part of Apple’s Public Beta program, include an “Update 1” reference in the title, suggesting that Apple may have originally intended to push out the third watchOS 4 beta alongside the corresponding iOS 11 and tvOS 11 betas, but held it back for further tweaking.
As expected at this still-early stage of a major OS update, the release notes list a long number of known issues that Apple has resolved since the last beta, with a decreasing number of issues that are still outstanding, mostly affecting developer APIs for third-party apps.