Accordions make most sense as a table of contents, although they are often used in FAQs. But in FAQs, you can't use the browser's search on page to find collapsed words. So you trade better scrollability for searching on the page. Not sure how many people use "search on page" on mobile devices though.
1 + 3 are great though.
I'm glad that you enjoyed 1 and 3 though - it's been really interesting seeing each person take something different away
Aside from that, something very weird is going on with the page. There’s a huge blank area to the right of the screen that you can easily scroll to accidentally. This also happens on Safari on macOS, where for some reason it doesn’t let you scroll back left (and persists the scroll position on page refresh?!).
I definitely agree with the blog post in general though - we should try to use HTML and CSS instead of always resorting to JavaScript.
Collapsable objects can be expanded by default as well, so not sure how relevant that is. I'd much rather a site use native techniques than load 100 JS frameworks in my browser to do something simple.