In either of those scenarios what power would the application developer have over the owner of the device? If the owner doesn’t like what the app is doing they’re free to remove it. There is no obligation to use that particular application to use the device for any purpose the owner sees fit.
AOSP is full open source mobile OS and uninstalling Google Chrome is as easy as uninstalling any other app and it can be replaced with any browser of the owners choice.
Similarly, SteamOS 3 is full Arch based Linux distro and uninstalling Steam is as easy as removing any package installed in Arch. Actually the immutable root file system does make it slightly more difficult, but it’s far from hard, and it can be replaced with a game launcher of the owners choice.
Proprietary software only becomes unethical when it is designed in a way that gives the device owner no option but to use it for their device to function as the owner desires.