I disagree - definitely not OK by me, though likely legal. People bought this because they wanted and paid extra for an internet connected device, and a regular thermostat is not that. I mean, would you be OK if your TV manufacturer disabled the screen and streamed radio stations instead?
I honestly can’t understand why anyone would be OK with it. I think our society has been getting trained to just accept whatever they throw at us. “Buying” something no longer means fully owning it, and I’m not OK with that, I just have to live with it.