You mean programs could access the file system normally? They were absolutely isolated as standard unix processes.
This is what I mean about iOSification - it's trending towards being a non serious OS. Linux gets more attractive by the day, and it really is the absence of proper support of hardware in the class of the M series that prevents a critical mass of devs jumping ship.
The only Unix security boundary is between users. There isn't a standard boundary between "a web browser tab" and "the file with your credit card info in it".
Programs absolutely could have much more controllable auto save before for when it made sense.