The reason to mention image posting is specifically to say that they want the UX to be like a text attachment rather than just a wall of text on someone's feed.

The reason to mention image posting is specifically to say that they want the UX to be like a text attachment rather than just a wall of text on someone's feed. Which is a much smaller disruption to existing experience. On that note, the fact that images are being used to show text content on Twitter right now is laughingly unfair to folks who use a screen reader, given how much we value HTML for its presentation flexibility.