Thanks Bob, I had misunderstood what "Enable Horizontal Swipe to Navigate Content" means.
My problem may be unrelated. When I am scrolling up or down an HTML article and then I swipe left or right I am able to jump to another article in the collection. It only happens on the HTML articles in the collection, and I want to disable this behavior.
The difference is that your InDesign article consists of multiple pages, so if you select the "Navigate Article Horizontally" option while exporting from InDesign, swiping left and right navigates to different pages within that multi-page article. This option is available for InDesign articles, but not for HTML articles, which are single-page.
The "Enable Horizontal Swipe to Navigate Content" option is available for collections, not articles. If you enable that option, users can swipe left and right to navigate away from the collection browse page. If you disable that option, users cannot swipe left and right to navigate between articles; instead, they must tap links to navigate.