These function are only available within Mobile device.
It would be really powerfull to have these in browser and in Windows MS Teams application.
I think throwing an error is too harsh.
It should at least use LocalStorage as a surrogate for the mobile's storage to make the functions run. Having to author multiple apps for different environments is sub-optimal.
Advanced users may prefer to develop complex interfaces one time only, and make it aware of screen dimensions to change object dimensions.
Currently there is not even a proper Boolean value to ask "IsBrowser", to make an If statement to avoid SaveData on browsers.