On google play it’s now possible to choose the form factor when uploading a new app version, in case there are both a “regular” app and the Wear OS - specific app.
It would be nice to be able to specify the form factor on the Google Play Deploy step in order to automate both the regular app and Wear OS app deploys independently. As of today it’s not possible to do that and there’s no alternative to having to upload the artifacts manually to google play for Wear OS.
Source: Manage your Wear OS releases on the Wear OS only track - Play Console Help