Screenshot: 9to5Google
It's unclear why it is taking Google longer to release this update, but more people are finally seeing the "Pixel Watch fully charged" notification on their devices. Once your watch completely charges, the Google Pixel Watch companion app will let you know. A server-side update has started rolling out to bring this to more users. If it hasn't made it to you, you can also check through the Bluetooth Quick Settings Tile or the Battery widget on your Pixel phone.