I think that is a major issue at the moment, the misleading UX aspect: I think I already elaborated it in my last bug report, but the position and the look of this (and the fact that it is there from the first page of the installation) makes users intuitively assume this is something to minimize/maximize the window or maybe to do some other settings of the window, but not that it is related to partitioning.
E.g., when trying to find the settings of a web page, I would never think of checking out the three min/max/exit buttons on the top right, or the “settings” button of firefox itself. Just an example to illustrate what I mean 
So some functions people complain about are already there, but we “intuitively don’t find it”. The result is, for many of us (if not most), this function is effectively not available.
Does it maybe make sense to make more tests about UX with a different approach? Not just ask users to click through the installation (which will users not make search for something like that), but tell users which features are there and ask them if they can test these features for you and if the features feel intuitive: so not provide information how to use or find these features, but just mention these features are existing and please test them for you.
E.g., as tests about this occur at the moment: if users now test, they might not find the partitioner, and just assume “ok, that’s not implemented yet I assume”, and then provide +1 feedback, not identifying the issue: they assume its on the roadmap, you assume it’s done → result is that nothing might happen. Maybe there are already other features with that issue too. Just a thought to improve