I think it got introduced a few months ago - IB switched their Cookie preferences tool to OneTrust and there was a bit of fallout with various features not quite working after that change, and it took a fews days of back-and-forth on the forum here to determine that it was linked to the new cookie prefs tool. I think the Do not sell thing is specifically a Cali law that they are complying with.

I don't usually use the desktop version but I have set my preferences to not permit any unnecessary cookies.