(1) (2) (3) (4)
and being anchor jumps to the relevant content is in line with the current horizontal flow. Part of my feeling toward this might also be from these two other factors:
1. A lot of text consumption is done on mobile platforms and, while I didn't check your site on mobile I am leaning more toward vertical infinite scrolling on desktop due to how many mobile things go that way today.
2. I tend to associate sites that page content and require horizontal movement with cheap advertisement exploitation - most times when something is delivering a big block-o-text as several pages it's either purpose built for or leverage to make sure they can cram as many ads as possible in the content.
So I guess my lean toward verticality is also a general usage expectation coupled with abuse of the horizontal flow.