There is no need to call update_screen() directly in an API function,
mode input processing invokes update_screen() as needed. And if the API
call is done in a context where redraw is disabled, then redraw is
disabled for a reason. A lot of API functions are of equal semantical
strength (nvim_call_function and nvim_execute_lua can also do whatever,
nvim_command is not special), this inconsistency has no purpose.