Thanks for the explanation!
I don’t know how other people use it, but in my usual workflow was to enter a folder, then scroll through the titles. If I saw one I wanted to read immediately, it was a tap to open the article. If I thought it was potentially interesting but would take more time to read, a quick swipe would save it without needing an extra tap or interrupting my scrolling. Then I’d mark the whole folder as read and move on. The saved stories are longer-form content that I read when I have more time to devote to them.
With the current behavior, if I swipe too fast it marks the article as read, and if I swipe slow enough just enough to open the buttons, it requires a little more accuracy to hit the “Save” button rather than the ones on either side. At the moment, I’m fighting years of muscle memory of a quickly stashing an article to be read later while perusing the feed. Change is hard! 
Just a thought: Would it be possible/easier to distinguish between fast and slow right swipes (like you have for left swipes) for go-to-feed vs. save story?