My wife and I have Series 6 Apple Watches. Until recently, we've been able to control our August 3rd Generation deadbolt locks withour watches and iPhones. This is a really convenient feature that keeps us from getting locked out of the house as long as we have either the phone or the watch with us.
Recently, we lost the ability to control the locks with our watches. I wrote August support and they're aware of the problem. August says the latest Apple device updates have made the watches unable to detect the locks. The phones still control the locks, however, so we haven't lost all functionality.
Our phones are at iOS 14.5.1 and our watches have Version 7.4.1 software. If you have these same versions of Apple software and August locks, you'll likely have the same issues.
Update June 16, 2021 - I got curious and tried using my watch to lock/unlock the August devices. Everything worked, so I check for app updates and found the August app had been updated. And no, August did not notify me of the update as they said they would.