Jam. I didn't read it as saying that the existence of jam positively and empirically correlates to a better shopping experience - the jam was used merely as an example - sample data, if you will - for demonstrating the central point that a proliferation of choice counter-intuitively causes less actual purchasing to be done than does an offering of fewer jams.
Jeans. The commenter quite correctly perceives that this is related to the jam. But the choice of product is, again, used to demonstrate that a rise in options has a point of diminishing returns beyond which customer participation decreases. I didn't interpret the article to hold the position that this was better, in any absolute sense, but that the negative experiences the writer describes were his attempt to make sense of, again, the phenomenon where too many choices makes people buy less.
This may be a phenomenon that, while it exists, not everyone experiences - that does not mean that the article is an attack on those people. And I think even people who enjoy as much choice as possible can still find the effect this article describes to be interesting, if only for how it seems inconsistent with what a purely theoretical approach would lead one to expect.
I didn't perceive that the author ever put forth the notion that less choice was better - if that assertion exists, it arises from one possible interpretation of the effect he describes.
These are my readings of the original article, and I share them with you as a perhaps useful guide for escaping the feeling the above comment seems to have, that there is inevitably a single and rather unpleasant attitude the author of the article could have had when creating this piece.