I'm not exactly sure what point you're trying to make here, but I don't think two different formats for encoding formatted text with images constitute different "mediums".
While you can produce identical outputs from the different methods, it's not hair-splitting to say that the authoring process and hence the nature of the medium to shape expression is affected by choosing one. When you opt towards maximizing generality your production cycle can grow without bound because everything is possible by layering different media, even if all of it is unnecessary. That's how you end up with creative projects that take multiple years to decades to accomplish.