Android Wear is now mainly used in smartwatches made by Asus (ZenWatch 2 and 3), Fossil (Q Founder, Marshal, Wander), Huawei (Watch), Lenovo (Moto 360 Gen 2, Sport), LG (Watch Urbane, G Watch R) and Tag Heuer (Connected).
It seems that this appears when setting up a watch using the Android P Developer preview build doing the rounds.
Google is well-known for constantly experimenting with new designs and UI changes, mostly via limited server-side tests.
The LG Watch Style - one of the first devices to feature Android Wear 2.0. Fashion brands continue to release new hardware running the OS, but it's been a hot minute since a major tech company has put any real time or effort into releasing new products with it. The reason for this is probably due to neutrality, same reason that Android Pay was rebranded to Google Pay which is because Android Pay could be used on Apple phones. 9to5Google adds that the notification was sent via Google Play Services, which is now at version 12.2 (most recent stable release).
Android Wear used to be my personal favorite wearable OS, and I religiously wore the Samsung Gear Live, Moto 360, and Huawei Watch.
It is also possible that perhaps Google could see a future in which its wearables operating system won't be based on Android, so moving away from the Android branding could be a way to make that transition.