Maybe those who are contesting develop performance is linked to screen size would provide us their work flow?
Render 1:1 previews, apply copyright metadata, apply generic keywords to shoot, apply custom develop settings (apply custom camera profile, CNR 25,CNRD 50,sharpen 49,radius 1.5, edge masking 22, detail 22)
Then work the images once they're all in and rendered fully.
What puzzles me is why anyone would think screen size isn't an issue ? It's fundamental to how much data has to be processed.
As a demonstration; open LR full screen (press F) then open an image in develop. Give the image maximum screen room (kill all the toolbars except the develop panel), now make some big changes to colour temperature and notice the lag in screen updates.
Then drop from full screen and make the LR window as small as possible, then repeat the CT changes. It's dramatically faster here.
It's important to remember that some of the people that have said there isn't an issue with performance probably aren't using it intensively at all or have very different expectations of performance.