It turns off your Sharing for what your playing for your session, but if you want to turn of the Sharing completely you have the option to do so.

For example I have a client who streams video games. He has a an on screen overlay that will show what track he is listening to so if his viewers what to know what he is listening to t will show and also be announced in chat. This is mainly done though the use of scrobbling the tracks to last.fm, now when they are not streaming they may not want the world to know what they are listening to this gives them the option to stop posting to last.fm and the Spotify profile until they have been inactive for 6 hours so they don't need to flip the switch back on.

You are not forced to link Facebook or Last.FM, you can unlink them ir prevent Spotify from posting to them.

The only one you are "forced into" is creating a Spotify profile. As you have said (or was it in the link to the request) anyone follow that profile but you can also stop posting what your playing there completely.

Think of this option of more of a standby then a off button. But the off buttons are still there.

If I'm misunderstanding your issue please explain. It reads from your post and the links in it that you take issue that Spotify can make your playing history public and you believe you can only turn that off on a per-session basis (private session gives a footer in the iOS app to so it's enabled), but going though my settings i can turn those features off completely.

Are you trying to stop Spotify recording your history completely from devices signed into the account. I.e. Make it so your computer can not see what tracks you are playing on your phone? Because I believe that is possible too.

I'm not sure how I did it, but I use the same account on my computer and phone (didn't need to sign into Spotify to play via my PS4 but I use the "devices" feature in the iOS app to send what I want to play to the console) and there have been times I've wanted to check my phones history on my computer (heard a track I like while out and about and wanted to put it into a playlist when I got home) but the history was only showing my playback for what I had played on the computer and not the phone. So this is speculation but maybe locking down the privacy settings makes the history only store on the device (ofcause I'm sure Spotify do record it because how else could they do their customised playlists, they also need to atleast keep a note of track plays to pay out royalties but from a privacy point of view Spotify don't have to pair that with a user account).

But the wording on the private session mode option you show says to enable it if you don't want to share your what you are listening too and it's under the social grouping of settings (that wording is missing from the iOS app) so my interpretation of that setting is that it's to do with the social features.

I'm just trying to better understand your complaint as my understanding is that you just need to deselect the other option(s) instead of enabling this one every session.