Well, "hope" is doing a lot of heavy lifting here. Google is still very much bound by the law regarding advertising and declaration of utility of sold product. The law gives them broad leeway as to the implementation, but if they decided tomorrow "hey you know how you can unlock your devices that we advertised as unlocked on our store? We changed our minds, the devices sold can no longer be unlocked," that would be grounds at the very least for return with refund, and a lawsuit if Google didn't honor that.