Huh. The UI on Medium is minimalist which means it may not be very discoverable, but my experience is it's very powerful. For example, if I click on a photo in one of my stories, this comes up. It gives me the option of wrapping text around the image (left option), aligning the width of the image to the text (second from left), making the image a little wider than the text (third from left), or full bleed (the one I have selected, far right).
I wrote a story where I set one of the images to have text wrap around it and it came out looking like this:
I didn't know you were also on Cake! Nice to see you in here.
This was such a good series. I enjoyed watching it when it was happening.