I think it's provably bullshit with a simple thought experiment - what happens when you make a site "sparse" (removing controls, more whitespace, less information density)? Things that used to take 1-2 clicks to do take many many more clicks, as menus get buried under sub-sub-sub menus now to accommodate all the space you just wasted. When I'm designing a UI for personal use, I design by how many clicks it takes me to do a common task. Any design implementation that increases that metric is a hard no to me. It's a very provable, easy metric. More clicks = less usability. Full stop. Especially when the clicks are hidden behind confusing and inconsistent icons that you usually have to guess the meaning of.