Apple has brought out the third build of watchOS 10.3, which is is now available for developer beta participants to download.
So far, it doesn’t seem like there are any major new features in watchOS 10.3, so it may end up being a bug fix and performance improvement fix release.
AppleInsider and Apple strongly suggest users don’t install beta operating systems or other beta software on “mission-critical” or primary devices, as there is the small chance of issues that could result in the loss of data. Testers should instead use secondary or non-essential hardware and ensure they have sufficient backups of their critical data at all times.