I don't agree at all.
Imagine a site selling "widgets" that differ in a few aspects, but are broadly the same. Each widget has a spec sheet, safety notice, etc. associated with it that could be 99% the same. That information is super-useful for users, because they could very well have come straight to that widget's page from the search engines (rather than navigating to it from homepage->category style navigation)
In other words, the user is coming fresh to the material and having all the details on that widget just a click away is great for providing reassurance in advance of a sale.
However, Google's spiders spider pretty much EVERYTHING.
So Google might see 1,000 near-identical pages in the case of 1,000 widgets being on sale on that site. Hence the need to block certain material from the spiders, not from users.