Not sure what the surprise is. It is a device that needs you to sign into an account and have an internet connection. Ie it is just a dumb terminal. Kind of like how Alexa speakers are useless without an internet connection. All the processing is done on servers.
Even if it was not an android app, you probably could have made a clone of it since you are basically interacting with a web api.
In their defence the device has the advantage of giving you instant access to their ai through the touch of a button whilst on phones you would need to physically open the app as the "assistant" functionality is already reserved to Siri, Bixby, etc. EDIT: I wasn't aware you can change assistants.
Personally I like the concept if the processing was done within the device, but considering you need monster machines to run llms I guess we are least decades away from that reality.