A "show more" button (or action) doesn't fix any of the problems associated with infinite scrolling of the type referenced in the linked article. The problem is not that the user doesn't need to do an action to scroll more, it's that
- infinite scrolling makes it impossible to maintain track of your position relative to the content (scrollbar is useless)
- it's impossible to have any idea how much content there is
- it's impossible to skip to a specific point in the content, both future (because it doesn't exist) and what has already been revealed (because it keeps moving)
- consequently it's impossible to link or bookmark a point in the timeline or leave the page and come back to it later
- browsers don't have good usability for ridiculously long pages
- because all the content already revealed remains the page constantly grows in performance requirements (memory requirements, CPU requirements because of active elements in posts, etc.)
That user has to perform an action (click or drag) to add more content to the page doesn't fix any of those issues.
Your timeline is very different however from the linked example, so the paradigm doesn't really apply. But... On your timeline some of the problems are slightly mitigated (because you can zoom out, and "today" makes a natural signpost, and because you can go a specific month, they are effectively virtual page numbers), but other problems still remain.
For instance, how do I know when the future events stop? How do I know that there isn't an event coming in 2 months' time ahead of my current scrolled position? 6 months? A year's time? Same goes for backwards.